ANIMAL KINGDOM.
WE embrace the earliest opportunity afforded by our alphabetical arrangement to present a few introductory observations in illustration of a science unrivalled in interest, and not greatly surpassed in importance by any department of human knowledge. ZOOLOGY, or the science which treats of the nature and history of animals (from ζῷον, an animal, and λόγος, a discourse), embraces so vast a field of observation, that although it cannot be regarded otherwise than as a single and beautifully connected science, its great extent of general doctrine, and multiplied variety of details, render necessary a subdivision into many branches, each of which, if worthily followed, is in truth more than sufficient to occupy the undivided attention of the most zealous votary. If in voluminous works exclusively devoted to natural history a single department of the science usually engrosses the entire attention of an author, it is evident that, in the present publication, it would not only be in vain to attempt a complete exposition of the subject under a single head, but that even the various treatises under which its different branches will be exhibited must be presented in a very abridged and compendious form. It shall be our endeavour, however, in the course of our natural history treatises, so to select and methodize the great leading facts of the science, as to enable our readers to form an accurate idea of the present state of zoological knowledge, even though certain minuter details, hitherto forming too conspicuous a feature of the subject, yet not essential to its truthful representation, should in some measure be curtailed.
With a view to obviate to a certain extent the inconvenience arising from the disconnection of the different parts of the science, which the nature of an alphabetic encyclopedia necessarily occasions, we now propose, under the words Animal Kingdom, to give, 1st, an exposition of such of
the general doctrines of zoology as, not pertaining more to one department than another, may with the greater propriety be separated from the history of particular classes, and presented as a useful and appropriate introduction to the whole,—thus uniting the advantages of an alphabetical and systematic arrangement; 2dly, to present outlines of some of the prevailing systems of zoology, so as to exhibit in a condensed form the general principles of classification, and enable the student more clearly to understand the relative connections which exist between the scattered treatises in which the subjects (in their alphabetical order) will be afterwards more fully developed; and 3dly, to give a sketch of the arrangement to be followed during the future progress of this work, which will not only serve as a guide or general index to the separate articles, but will, on the completion of the Encyclopædia, enable the attentive reader to methodize these articles in such a manner as to form a complete and consistent system of zoology.
It is by no means so easy as it may at first appear, to define precisely what is meant by the term animal, because, as we descend in the scale of beings, we find a transition so gradual from those whose powers and properties are strongly characterized, to others which, along with a scarcely perceptible share of sensation and voluntary motion, partake so greatly of the nature of plants, that the most acute naturalists have varied in opinion regarding the exact line of their demarcation. There are also many plants which appear to differ less from certain animals than they do from other plants of an opposite nature and construction. This connected series of organized bodies, however, is not graduated after the mode established by some vague writers on natural history;
Animal Kingdom. for it is not the most perfectly composed, but rather the least complex plants, which follow the most simply organized animals. It has been said that nature follows a continuous and ascending chain, from the mineral to the plant, and from the vegetable to the animal kingdom, the apex of which is crowned by the most perfect work of creation—the human race. Certain minerals, such as amianthus or asbestos, no doubt exhibit a fibrous or woody structure; and coral, which has a stony texture, a vegetable form, and polypus inhabitants, has been adduced in illustration of the union of the three kingdoms.1 But all such fanciful speculations are the result of partial and inaccurate observation. The calcareous basis of the coral is formed by a species of polypus, and has no more principle of increase in itself than the shell of the oyster or the waxen cells of the honey-bee. Its elegant branches are created by the instinctive labours of the animal inhabitants, which alone are possessed of life. The animal and vegetable kingdoms are more correctly compared to two great pyramids, intimately united at their bases, but diverging more and more as they ascend.
The extraordinary beings which by their ambiguous nature may be said to have thus blended two kingdoms into one, are called zoophytes or animal plants. They were arranged by Tournefort among vegetables, and were at an after-period removed to the class to which they really belong, chiefly on the authority and through the labours of Linnæus and Pallas. These naturalists bore in mind what few of their predecessors seem to have remembered, that locomotion, that is to say, the movement of a body from place to place en masse, though a general characteristic, is not an essential or indispensable attribute, of animality; for numerous animals of the molluscous and radiated kinds are as permanently fixed to their native rocks and coral reefs as the most deeply rooted plants are to the soil which gave them birth.
As sensation and the power of voluntary movement, in whole or in part, are the principal characteristics of animals, it is evident that the more these faculties become developed, the greater will be their removal from the vegetable kingdom. The more perfect the plant, and the more complicated the animal becomes, the greater disparity will be perceived to exist between them. If, in distinguishing the animal from the vegetable, nothing more were required than to point out the differences between an oak and an elephant, the line of demarcation would be easily drawn, and the characters of the respective classes could never more be confounded. But there are many plants which, though less aspiring than the oak, lay claim to a closer alliance to a higher kingdom; and many animals of a more carnivorous nature than the elephant are much more nearly connected by their nature and attributes with the vegetable tribes. When we perceive a living or animalized substance producing by suckers, buds, or offsets from its own body,—when we see that by the influence of light, air, and humidity, it is rendered capable of re-assuming the functions of vitality after a long period of suspended animation and apparent death,—when we ascertain that it cannot live except in water, or when saturated with moisture,—and that although it may be capable of certain languid and partial motions, it is yet fixed for life to a single point of space, where it derives its nourishment by means of external pores,—we have certainly the description of an animal of the lowest order, which applies at the same time almost equally well to vegetable life.
The following were the dicta of Linnæus in relation to
the three kingdoms of nature:—"Minerals grow; vegetables grow and live; animals grow, live, and feel." The only character common to these kingdoms, according to the above definitions, is that of growth, or the power of adding to previous bulk. "The vegetation of stones," it is observed by the late bishop of Llandaff, in his Chemical Essays, "hath been admitted by many; and some have contended that minerals, as well as animals and vegetables, spring from seed, the greatest being nothing but the expansion of the parts of a minute grain of sand." But mineral bodies in truth cannot be said to grow. They receive by aggregation or superposition, by mechanical or chemical agency, an increase of particles. Tournefort, indeed, was of opinion that stalactites in caves actually increased by an internal growth or propulsion like that of plants and animals. But it is known that these concretions add to their bulk by successive depositions of stony particles contained in the water which bathes their sides or percolates through the canal by which their centres are frequently perforated. They possess no attribute which bears the slightest affinity to that internal life which propels the fluids or assimilates the nutritive juices in the animal and vegetable kingdoms. Minerals, then, are destitute of that active power by which animals and plants effect an individual appropriation of such materials as conduce to their nourishment and increase, and which is carried on, not by casual juxtaposition, or the addition of similar particles previously prepared, but by an admirable and elaborate process, through which the ponderous bullock, with its immense load of fleshy fibre, converts into its own muscular and sanguiferous system the sweet-smelling grass of the meadow; and through which also the size and flavour of our most delicious fruits are often primarily derived, from an addition to their natural soil of substances of a very different and less inviting nature. Romé de Lisle has accurately observed that straight lines and plane surfaces are characteristic of mineral bodies, but that animals and plants are composed of curved lines or rounded surfaces, resulting from that central power of life which dilates the internal organs in all directions, and tends to produce spherical or cylindrical forms. The seeds of plants, the eggs of birds, and the young of all animals, are remarkable for the roundness of their outlines.
The objects of natural history, however, are not now divided into three kingdoms; for the characters which connect together plants and animals on the one hand, and distinguish both of these kingdoms from minerals on the other, are so obvious and strongly marked, that the divisions now established are those of organic and inorganic bodies; the former including all animals and plants, the latter all mineral substances. The definition of an animal, given by M. Virrey, is as follows: A being, organized, sensible, endowed with voluntary motion, and provided with a central organ of digestion. And he thus defines a plant: A body, organized, insensible, not endowed with voluntary motion, nourished by external pores. To these he adds another character, that the reproductive organs of plants are developed and thrown off every year, whereas those of animals are persistent. It is evident that the last clause of his first definition—that which relates to the central organ of digestion—if rigorously applied, would exclude a number of the infusorial tribes from the animal kingdom.
Perhaps the most efficient mode of distinguishing between animals and plants is by having recourse to a certain range of characters, derived from the study of their
Animal Kingdom. internal structure and organic functions: thus the possession of nerves, muscles, and a stomach, with the consequent attributes of sensation, voluntary motion, and digestion, will be found to separate animals properly so called from all other organized matter. If these leading characters are not common to all animals, they are at least proper to them alone; and if the whole of these characters are not always united in the same animal, we invariably find at least one of the three. Thus certain species of polypus, the sensibility and voluntary movements of which cannot be said decidedly to manifest themselves, are obviously furnished with a digestive cavity or stomach; and many of the infusory animals, of the digestion of which we know nothing, are as perfect in regard to their varied powers of locomotion as any of the higher classes. Numerous zoophytical species, indeed, are of so simple a nature, that in them we cannot perceive either a distinct tissue or a nourishing fluid; but we can form some opinion of the nature of their elements from the character of their properties. Irritability indicates nerves, motion supposes the existence of muscles, and the continued maintenance of life attests nutrition. Thus the materials of animal life, so vaguely constituted in these creatures, are detected by their general properties.
In relation to their chemical characters, animals may be said to be principally composed of azote; and vegetables, with the exception of cruciferae, of carbon. Animals absorb oxygen, plants disengage it; the former reject carbon, the latter become impregnated with it. An exchange of principles is thus effected between the two great divisions of organized existence; but it has been observed that plants merely fix or organize carbon, whereas animals appear to transform into azote, both the air which they respire, and the aliments by which they are nourished.
It has been asserted that a single mouth, or opening to the digestive canal, sufficiently characterizes animals from plants, as the latter always possess innumerable pores, which with them are the representatives of the mouth, and conduce to the same ends; but this distinction is in fact inaccurate, as some species of Fasciola possess two mouths, certain Tristoma three, and the genus called by Cuvier Rhisostoma many more; to say nothing of the infusorial tribes, many of which have no mouth at all, but derive their nourishment by imbibition through the medium of external pores. Nutrition, or the power of deriving nourishment from other bodies, is common alike to plants and animals, and effects for organized and living bodies that increase of bulk which inorganic or disorganized substances can only attain through the medium of an affinity of particles, or by mechanical aggregation. The functions of nutrition, however, as manifested in the animal and vegetable kingdoms, are very differently performed in each. Fixed for ever to the soil which gave them birth, plants are rendered incapable of searching after nourishment by a voluntary change of place, but derive their chief support from roots, the pores of which absorb the nutritive portions from the humid soil, and by a uniform and continuous action, which is only interrupted by an absence of the necessary moisture. The generality of animals, on the contrary, being possessed of the power of locomotion, are also endowed with the capacity of transporting with themselves a supply of necessary nourishment; for which purpose they are provided with an internal cavity or stomach, the inward surfaces of which are provided with absorbing pores, which Boerhaave expressively named internal roots. "The magnitude of this cavity," observes Cuvier, "in a number of animals, per-
mits them to introduce solid substances into it. It was necessary then that they should have instruments for dividing those substances, and liquors for dissolving them. In a word, with such animals nutrition does not immediately commence upon the absorption of the substances which the soil or the atmosphere furnishes. It is necessarily preceded by a vast number of preparatory operations, the whole of which constitute digestion.1 The motion of the nutritive fluid in plants, from the simplicity of their structure, and the fixity of their position, seems to be preserved by simple external agents. "It appears to proceed upwards by the effect of their spongy or capillary texture; and the evaporation which takes place at their top, and its motion in that direction, is the more rapid in proportion as the evaporation is great. It appears also that the motion of this fluid may even become retrograde, when it ceases to flow in its usual course, or changes into absorption by the coldness and humidity of the atmosphere."2 In regard to animals, however, the case is different. Being destined continually to change their localities, and to live exposed to a variety of temperatures, they require an active principle within themselves for the conveyance of their nourishing fluid. This fluid is therefore contained in a multiplicity of canals, which are ramified from two trunks, communicating with each other in such a manner that the roots of the one, called the venous system, receive the contents which the other, known as the arterial system, has propelled to the extremity of its branches, and restore them to the centre, from which they are again driven forward. It is this rotation which constitutes what is called the circulation of the blood. It may be regarded as a function of a secondary order proper to animals, but not universal to that kingdom, as it depends in a great measure on the existence of that central organ called the heart, of which some classes are entirely destitute. It is therefore less essential to life than digestion, and not so intimately related to the faculties of sensation and locomotion. In regard to respiration, animals which are unprovided with a regular circulating system respire, like vegetables, over the whole of their surface, or by various vessels which are placed at different points, and convey the air to the interior of their bodies. "No animals," says Cuvier, "respire by a particular organ, except such as have a real circulation; because in them the blood coming from one common source, the heart, to which it constantly returns, the vessels that contain it are so disposed that it cannot arrive at the other parts until it has passed through the lungs. This, however, cannot take place in vegetables, or in those animals in which this fluid is everywhere diffused in a uniform manner, without being contained in vessels." Pulmonary or branchial respiration is therefore an animal function of a third order, invariably connected with circulation, and one degree removed from such faculties as are essential to animal life.
When a vegetable dies of old age, it begins to decay in the centre. We frequently see ancient willow-trees entirely dead, except in a few slender twigs, or in small portions of their superficial bark. An animal, on the contrary, first dies in its extremities and circumference, whilst the heart or central portion continues for a time to perform, however languidly, its accustomed actions.
Among plants both sexes usually occur in the same individual, or even on the same flower; but in a far greater proportion of animals the two sexes are represented by separate individuals. There is indeed no genuine hermaphrodital union among mammiferous animals, birds, reptiles, fishes, cuttle-fish, crustacea, or in-
1 Lectures on Comparative Anatomy, lecture 2.
2 Ibid.
Animal Kingdom. Among many molluscous animals, however, such as the oyster and other bivalves, both sexes are found on the same individual, which is consequently sufficient of itself for the purposes of reproduction, and may be regarded as a genuine hermaphrodite. This singular order of things is in fact indispensable to the nature of bivalve testacea, which, being almost entirely deprived of the power of locomotion, and destitute of eyes or other organs by which to distinguish each other, require to possess within themselves the power of reproduction, lest their kind should cease. The species is both represented and continued by a single individual. In the earthworm, again, the same union of the sexes occurs, but modified in such a way that the concurrence of two individuals is required for the continuance of the race, and each acts in relation to the other both as male and female. This is also the case with slugs, and a great proportion of univalve and turbinated shells. Lastly, the zoophytical animals are not distinguished by any sex, but are multiplied by separation or excision of parts of their own bodies.
The law which establishes a perfect distinction and separation of the sexes in animals seems likewise to produce a double and symmetrical structure, and is of great extent in that kingdom; whilst the circular or radiated form more especially distinguishes plants, and is also characteristic of those zoophytical tribes which, both by name and nature, claim an alliance to the vegetable world.
The grain, and the fruit or kernel, may be said to bear the same relation to a vegetable as the egg or the embryo does to an animal,—with this difference to be borne in mind, that the concurrence of the sexes is necessary to the formation of the vegetable egg, whereas in the animal kingdom that circumstance is indispensable only to the fecundation of the pre-existing germ. The perfection of a plant, and the ultimate aim of its existence, if we may use such a phrase to an inanimate structure, consist in the continuance of its kind. In such as are named annuals especially, the term of whose existence is limited in many instances to a small portion of the year, the ripening of the seeds is speedily effected, and, after a very brief period, death succeeds “the bright consummate flower.” In numerous tribes of insects the same fleeting existence is observable, though the ephemeral nature of these last-named tribes is rather apparent than real, as the wonderful metamorphoses to which they are subjected conceal their identity from the eye of the uninitiated, and greatly interfere with a continuous tracing of the same individual from the egg to the perfect form. For example, many aquatic flies, such as the Ephemera and others, whose declared and more obvious existence does not exceed a few hours, have, previous to their assuming the winged state, spent months or even years in the banks of rivers, and beneath the surface of the stream.
Even the mode of reproduction among the lower tribes of the animal kingdom bears some analogy to that of vegetables; and as the vital principle in the smallest branch or portion of a willow-tree is easily continued and increased though separated from the parent stem, so in many zoophytical animals a bud, branch, or other section, removed from the full-grown individual, suffers no injury from such partition, but, on the contrary, acquires almost immediately a complete and independent power of existence within itself, and is ere long capable of exercising or enduring a like division in favour of posterity. Animals as well as plants are liable to be affected by the revolutions of the seasons; for the period of flowering in the one class is answered by the season of love in the other, and the fall of the leaf is only analogous to the periodical renewal of the feathers of birds and the hair of quadrupeds. The platanus quits and renews its superficial
bark, while serpents and cray-fish cast off and reproduce their scaly and crustaceous covering. To be produced and nourished, to increase, to engender, and to die, are characters common to every class of organized existence; but animals properly so called are alone endowed with instinct and voluntary motion,—they alone possess nerves, muscles, digestive organs, and blood, with the faculties of perception, &c. consequent on these attributes.
The preceding observations will serve to illustrate the principal relations and analogies which exist between animal and vegetable life. But there are other characters proper to animals, the whole of which, however, are not universally bestowed on that class, of which it will now be proper to say a few words. The substance of which even the most perfect animal is composed may be resolved into four tissues,—the cellular, the muscular, the fibrous, and the medullary.
The cellular tissue is the most extensively bestowed, and forms, according to an expression of the French physiologists, the canvass of all the organs, and of every animal. It is even common to vegetables, and serves at once to compose, to unite, and to separate the organs. Formed of laminae or plates interlacing each other in every direction, and perforated by small cavities which have intimate communication, it also sometimes presents itself under the form of membranes, which, when they assume a tunnelled or cylindrical shape, are denominated vessels. It is in this tissue that the gelatine accumulates for the formation of the cartilages, and the calcareous salts for that of the bones. It is amongst its meshes that the fat is amassed, the small vessels distributed, and warmth developed. It forms the basis of the organs.
The muscular tissue is composed of fibrin, and its chief property is that of contraction. It forms what are called the fleshy parts of bodies. Bundles of this tissue crossing each other compose the heart, and, under another aspect, form the stomach and intestines. It is the agent of movement.
The medullary or nervous substance is composed of a soft albuminous pulp, and is protected by powerful membranes. It enjoys the admirable faculties of perceiving, comparing, judging, remembering, and willing; it gives to the senses their special properties, to the muscles their moving force, and is the seat of that mysterious union between mind and body through which the intellectual faculties result or become manifested, and the exact nature of which the most acute of metaphysical inquirers, and the most accurate and thoughtful observers of nature, have as yet sought in vain to illustrate. Sensation is the attribute of the nerves.
The fibrous tissue, the most resistant and unfeeling of all, fastens the bones to each other, and connects the bones and the muscles. It forms the ligaments, the tendons, many vessels, and some resisting membranes employed for the protection of the more important organs. In composition it approaches the cellular tissue, but its properties are dissimilar. Its character is resistance.
Each of these tissues is destined to the performance of a special purpose: The cellular organizes, the muscular moves, the nervous perceives, the fibrous attaches and resists; but one and all are under the influence of that nourishing fluid, so different in various animals, known by the name of blood. This fluid is red, circulating, of a high temperature, in animals of the superior classes—that is, the mammalia and birds; less red, colder, and not so charged with oxygen, in fishes and reptiles; colourless, but still circulating, in the mollusca; without either colour or movement in insects; scarcely perceptible in certain worms; and apparently wanting in zoophytes. It is this fluid which animates all the organs, and presides over
Animal Kingdom. every function. Nutrition exhausts its principles, digestion repairs them, respiration elaborates and renders it perfect, and the action of the heart gives it circulation.
All these elements united and variously combined compose the different organs of animated beings, the harmonious action of which organs forms the essence of our wellbeing, physically considered, in the present stage of our existence. The human race possesses the attributes of animal life in common with the brute creation; but we must ever bear about with us a firm conviction that these are "the accidents, not the essentials of our nature;"1 and that however proper it may be to mention them as the technical statements of physiology, yet that they are totally inadequate to the description of a being who bears about with him the germ of immortal life, and knows that he was created "but a little lower than the angels." "Those persons," says Buffon, "who see, hear, or smell imperfectly, are of no less intellectual capacity than others; an evident proof that in man there is something more than an internal sense. This is the soul of man, which is an independent and superior sense, a lofty and spiritual existence, entirely different in its essence and action from the nature of the external senses."
It is easy to perceive that one set of organs may be so related to another as constantly to require its co-existence. Thus, circumscribed respiratory organs are always accompanied by a heart, which causes the blood to flow through them; and a brain is never found without nerves and muscles, which serve it as faithful ministers and attendants. The brain receives impressions, and is enabled to judge of them through the medium of nervous sensations: this is the first mode of the functions of relation. But the order is inverse so far as relates to the phenomena of the will as connected with the exercise of the voice and the organs of movement. The brain wills or commands, the nerves transmit the order, and the muscles execute it.
There are other co-existences in the animal economy as apparent as those above alluded to, the motives of which are not, however, so easily comprehended. We are still ignorant why the viscus called the liver should always exist where there is a heart; and why all orthopterous insects should have the forehead furnished with a broad plate.
It will readily be conceived that the diversified circumstances of life in the various tribes of animals necessitate an infinite variety of phenomena in their functions and faculties. An animal which respires, and has its dwelling in the waters, can neither feel nor move after the manner of one which breathes in the pure air; and wherever there are branchiae or gills instead of lungs, we are sure also to find oviparous generation, an incomplete circulation, an absence of voice, and imperfect organs of hearing and of smell. But the existence of lungs alters the relation of the whole of these functions.
The same principle may be applied to the different kinds of aliment. A carnivorous animal is endowed with force and courage: it has a strait stomach, short intestines, and a lank or somewhat slender form. Herbivorous animals, on the contrary, are usually mild and timid, dull in action, of a sluggish nature, and unapt to self-defence: their intestines are spacious, and their external forms more or less massive. "The disposition of the alimentary canal determines, in a manner perfectly absolute, the kind of food by which the animal is nourished; but if the animal did not possess, in its senses and organs of motion, the means of distinguishing the kinds of aliment suited to
its nature, it is obvious that it could not exist. An animal, therefore, which can only digest flesh, must, to preserve its species, have the power of discovering its prey, of pursuing it, of seizing it, of overcoming it, and of tearing it in pieces. It is necessary then that this animal should have a penetrating eye, a quick smell, a swift motion, address and strength in the jaws and talons. Agreeably to this necessity, a sharp tooth, fitted for cutting flesh, is never co-existent in the same species with a hoof covered with horn, which can only support the animal, but with which it cannot grasp any thing: hence the law according to which all hooved animals are herbivorous, and also those still more detailed laws, which are but corollaries of the first, that hoofs indicate molar teeth with flat crowns, a very long alimentary canal, a capacious or multiplied stomach, and several other relations of the same kind."2 In short, such harmony exists between the different organs, according to the leading forms after which they are modelled, that an experienced anatomist, from an inspection of a very limited portion of a body, can form an accurate opinion regarding the entire characters of an animal. It is thus that Cuvier, combining profound knowledge of detail with a commanding power of generalization, has, as it were, called back into existence those long-extinguished races whose scattered and imperfect remains attest the wonderful revolutions to which our planet has of old been subjected.
The aid which natural history has derived from the sister sciences of anatomy and physiology, is in nothing more apparent than in the improved systems of modern classification. It was formerly the practice to adopt, as the basis of arrangement, the modifications of some single organ, chosen arbitrarily and at hazard. Of course it did not follow that all the other organs would resemble each other in all the animals in which the likeness of this one organ might be preserved. Nothing, therefore, could be affirmed respecting the other organs belonging to the whole of a class or genus of animals, which we should have attempted to distinguish by characters taken from this unimportant organ. "Suppose, for example," says Cuvier, "that we had made three divisions of animals, the aerial, terrestrial, and aquatic, as they were anciently classed; there would be included in the first class, besides what are commonly called birds, some mammiferous animals, such as bats—some reptiles, as the dragon—some fishes, as the flying fish—and an infinite multitude of insects. Similar difficulties would occur, in a greater or less degree, in the other two classes." "This example is well calculated to show how important it is that the characters of our divisions should be well chosen; for, though in the formation of methods and systems of natural history, errors so flagrant as the above are not now committed, several naturalists, even in modern times, have adopted divisions which, in the detail, tend to similar results."3
It is both interesting and important to trace the different systems of organs in the animal kingdom, from their first feeble rudiments, through a gradual and long-continued chain of increasing manifestation, to their complete development in some particular class or order, in which the perfect exercise of a special function is indispensable to its wellbeing. It is in accordance with such development that the improved classifications of recent times have been established; and it is now admitted as an axiom, that a natural and philosophical arrangement of animals can have no other foundation than a knowledge more or less perfect of anatomical structure. It does not follow from this that every naturalist must be a profound
1 Grinfield's Letters to Lawrence.
2 Lectures on Comparative Anatomy, vol. i. p. 56.
3 Lec. cit. p. 62.
Animal anatomist; for such is the multiplicity of details connected with the history of the haunts and habits of species, and with the discrimination and description of their external characters, which in truth form the proper object of the zoological inquirer, that a much longer period than that allotted to the life of man would be required likewise to ascertain the distinctions of internal structure, were it necessary to apply anatomical science to all the minor details, or even to the less important divisions, of natural history. But the beauty and excellence of the anatomical system consists in the admirable co-ordination of characters which it exhibits, and through which, with rare exceptions, we are able to arrange the subjects of investigation in a natural manner, even according to their external aspect, as soon as we have established certain great leading principles of classification drawn from the facts of anatomical science. The more essential and important characters even of internal structure are manifested externally by the influence which they exert over more obvious though less dominating attributes; and thus, even in the absence of a positive and direct knowledge of general laws, these are indicated with wonderful certainty, though somewhat empirically, by means of superficial observation. It is thus that, through the combined efforts of the naturalist and anatomist, the convenience and facility of application which characterize artificial systems, and constitute indeed their sole value, may be combined with that philosophical accuracy and consonance with the march of nature which results from deeper and more substantial views.
The object of every good method, according to Cuvier, is to reduce a science to its simplest terms, by reducing the propositions it comprehends to the greatest degree of generality of which they are susceptible. A good system must therefore be such as will enable us to assign to each class, and to each of its subdivisions, some qualities common to the greater part of the organs. This object is to be attained by two different means, which may serve to prove or verify one another. "The first, and that to which all men will naturally have recourse, is to proceed from the observation of species to uniting them in genera, and to collecting them into a superior order, according as we find ourselves conducted to that classification by a view of the whole of their attributes. The second, and that which the greater part of modern naturalists have employed, is to fix beforehand upon certain bases of division agreeably to which beings, when observed, are arranged in their proper places. The first method cannot mislead us, but it is applicable only to those beings of which we have a perfect knowledge; the second is more generally practised, but it is subject to error. When the bases that have been adopted remain consistent with the combinations which observation discovers, and when the same foundations are again pointed out by the results deduced from observation, the two means are then in unison, and we may be certain that the method is good."
The true distinction between the value of an artificial and of a natural method in zoology consists in this, that the former teaches us little more than the name of an animal, whereas, in relation to the other, we have no sooner ascertained the name of a species, or its position in the system, than we become at the same time acquainted with numerous facts in its character and history, which we never could have discovered, except by actual observation, had it formed part of those miscellaneous and falsely connected groups which so often constitute the divisions of an artificial system. A natural arrangement is also of
great advantage in facilitating general views, by rendering a single animal a type or representative of many, as containing in itself the essential characters of a numerous tribe; and thus the whole animal kingdom may be represented by a few hundred species. By a too strict adherence, however, to the natural method, we are apt to lose the advantage of precision in individual definitions, and, in the case of the numerous transitions, find ourselves unable to fix any limits, if these have not been already established by nature. To discover a medium between these two methods, so as to unite the advantages of each, is now more than ever desirable in the formation of systems.1 He indeed who flatters himself with the idea that the families, tribes, genera, and sections, which he has laid down on paper, are so many natural divisions, can only be compared to the person who, because he may find the meridians and other circles of an armillary sphere convenient for the division of the heavens, should therefore imagine that they must exist in nature. "In one and the other case," Mr Macleay observes, "artificial modes of distribution are resorted to, which, however ingenious in themselves, are but sad proofs of the limited state of our faculties, when we consider, that without such instruments the vastness and sublimity of the creation cannot be comprehended." (Horæ Entom.) There is in fact no such thing as classification in nature. In the animal as well as in the vegetable kingdom certain species are grouped together by such analogies of form and structure, as to render their mutual resemblances apparent even to an ordinary observer. To these groups the name of natural families may, without impropriety, be applied; but that no general system of arrangement exists in nature, by which the various genera may be made to follow each other, like the links of a linear chain, is evident from the discordant, ever-varying, and frequently arbitrary methods employed even by the most accomplished naturalists of the day. We must probably rest satisfied with such a system as presents the objects of natural history in conveniently arranged groups, the component parts of each of which bear a considerable resemblance to each other, without seeking after what is unattainable, namely, the establishment among these groups of a perfectly natural and well-graduated sequence. "When there are," says Mr Vigors, "no absolute divisions except species in nature—and this, from every observation I have been enabled to make, I firmly believe to be the case—every division which we are forced to institute in our arrangements for the convenience of illustration, and indeed for the purpose of mutual communication with those who are engaged in similar researches with ourselves, must be to a certain extent arbitrary and artificial; and every inquirer into nature may cause the line of demarcation that separates his conterminous groups to infringe more or less on the limits of either, according to his peculiar mode of viewing his subject."2
No satisfactory argument can be adduced to prove, as some have imagined, that the specific differences of animals have resulted from the lapse of time, and the effects of climate, or other secondary causes. The variation of specific character, though sometimes remarkable, is restricted; and Cuvier has shown, from a minute examination and comparison of mummies of the ancient Egyptian Ibis with individuals of the modern race, that in regard to that species no perceptible change has taken place during the last three or four thousand years. The original creation of distinct and predetermined species is the rational and well-founded belief of all who have studied the
1 See Carus's Introduction to Comp. Anat., translated by Gore.
2 Linnean Transactions, vol. xiv. p. 512.
subject with attention, unbiased by any prejudice in favour of imaginative views, which have no foundation in the facts of nature. "It is certain by revelation," says Buffon, "that all creatures have equally participated in the favours of creation; that the first two of each species were formed by the hands of the Creator; and we ought to believe that they were then nearly such as they appear at present in their descendants. We must also consider, that although nature proceeds by gradual, and frequently by imperceptible degrees, the intervals are not always the same. The more exalted the species, the fewer they are in number; and the shades by which they are separated are more conspicuous. The smaller species, on the contrary, are very numerous, and have more affinity to each other, so that we are the more tempted to confound them together in the same family. But we should not forget that these families are our own works; that we have made them for the ease of our memories; and that if we cannot comprehend the real relations of all beings, it is ourselves, not nature, that are in fault; for she in truth knows not our pretended families, and recognises individuals alone."
Omnipotence, the first, the greatest, and indeed the only truly creative power, formed the species of animals; and the influence of man and of physical agents has produced the varieties. But it is only superficial characters which either the one or the other of these ulterior causes has the power of modifying. The basis of organization, or real specific mould, remains unalterable, though a thousand circumstances constantly tend to produce variations in the external forms. Of these circumstances the most powerful is no doubt climate; under which name it is necessary to comprehend the differences of local situation and temperature, the nature of the soil and its productions. It is climate, in the first place, which chiefly determines the geographical position of animals, and thus commences the action of the modifying powers. The nature of their food is also highly influential; and as it depends so immediately on the qualities of temperature and soil, the climate is still the modifying cause. If the same animals usually accompany the same vegetables, it is because the constitution of both demands similar influences, and because through each other they are both dependent upon the same support. Certain animals are leagued with certain plants, and these again with certain soils and climates; and a careful observance of these mutual dependencies exhibits one of the finest and most beautiful harmonies of nature. This, however, is not the place in which to discuss the intricate and important subject of the geographical distribution of animals.
Certain original forms have been continued since the creation of organized beings, and all the individuals which represent or belong to one of these forms constitute what is called a species. The slighter differences which occasionally prevail among the individuals themselves, independent of the customary distinctions of age and sex, are called varieties. Such varieties are seldom permanent, and are usually lost by the progeny re-assuming the ordinary and characteristic form or colour, except in some remarkable instances, such as the horse, dog, and other long-domesticated species, of which man has so thoroughly altered the original condition, as to have impressed them with a second and more pliant nature. An individual, according to Buffon, is a separate detached being, and has nothing in common with other beings, excepting that it resembles, or rather differs from them. All similar individuals which exist on the earth are considered as
composing the species of those individuals. Yet it is neither the number nor collection of similar individuals which constitutes them; for a being which existed for ever would not be a species. "Species then is an abstract and general term, the meaning of which can only be determined by considering nature in the succession of time, and in the constant destruction and renewal of beings;" and it is by comparing the present state of nature with the past, and actual individuals with their predecessors in kind, that we come to attain a clear idea of what is called species; for a comparison of the number or resemblance of individuals is only an accessory idea, and frequently independent of the first. The ass resembles the horse more than the barbet the greyhound; yet the latter are but one species, since they produce a fertile progeny; but the horse and the ass are certainly of different species, "since they produce together vicious and unfertile young."
It is indeed difficult to define the term species, otherwise than as an assemblage of individuals descended from common parents, which bear as great a resemblance to them as they do to each other. Species then are distinguished by fixed forms, which, though to a certain extent alterable, and for a limited time, by external or accidental causes, are yet handed down unimpaired from generation to generation; and although certain species seem to have disappeared entirely from the earth, in consequence of the great natural catastrophes which have taken place in ancient times, and the local distribution of many still existing races has been modified or changed by the influence of man no less than by the accidents of nature, there is no reason to believe that any one species has sprung from the gradual alteration of another, or that the circumstances under which an individual may have been at first casually placed were sufficient to develop both form and function, without an impress from a higher and more powerful hand, by which it was fitted to perform its part (pre-ordained) in the great theatre of the world.
Animals which by their union produce fertile individuals, are generally reputed of the same species. This law of nature, as it was formerly called, having been found to admit of certain though rare exceptions, is not now so broadly insisted on as a test of specific identity as it was in preceding times. But it appears, from the result of numerous experiments, that the generality of animals produced from a cross between even the most nearly allied species, are either altogether incapable of reproduction, or fertile in so imperfect a degree, that their descendants speedily become entirely sterile. It has been said that birds alone were unsubjected to this rule, and that hence has arisen the wonderful variety which that beautiful class exhibits. There is no doubt of the occasional fertility of their hybrids, as in the case of those mule birds produced between the goldfinch and canary; but as it has not been proved that such unions of distinct kinds ever take place when uncontrolled by the depraving influence of domestication, there is no reason to attribute the origin of any of those species or varieties which are known to exist in a wild state to any such improbable alliance.
It is known that a productive union may take place between animals of a different species, provided such species belong to what naturalists call the same natural family. Thus the ass and the mare, or the horse and the female ass, produce the well-known animals called mules: the zebra also produces both with the horse and the ass; but in order to deceive the female zebra, it is said to be necessary to paint the hides of the former with those bizarre colours which adorn her accustomed mate.1 It is probable,
1 Dict. Class. d'Hist. Nat. tome I. p. 48.
Animal Kingdom. however, that all these unions are so far forced and unnatural, that they never take place except through the influence of man, when domestication, and the numerous changes consequent upon it, have altered or impaired their natural instincts; for it has been observed that, however education may perfect certain special qualities, which man has the art to render subservient to his own convenience, yet a more extended view of the effects of domestication will convince us, that it is almost always to the disadvantage of their natural capacities that the brute creation are made to borrow the mask of human intelligence.
Buffon appears to have adopted from Ray a rule which many now regard as inaccurate and artificial, but which he made use of to determine the identity of animal species, viz. "any two animals that can procreate together, and whose issue can also procreate, are specifically the same." In this, however, it has been observed that he contradicts himself by afterwards admitting that the sheep and goat are of different species, at the same time that he asserts that the he-goat and the ewe produce a mixed breed which continue fertile for ever. Dr John Hunter (a great authority) was also of opinion that the true distinction between different species of animals must ultimately be gathered from their incapacity of propagating with each other an offspring capable of again continuing the kind. Thus the horse and ass beget a mule capable of copulation, but incapable of begetting or producing offspring. The accident of a mule breeding, according to the same authority, even if it were proved, would only show that as many perfect animals of true species and distinct sexes are incapable of breeding at all,—(thus showing that nature, even in her greatest perfection, sometimes deviates from general principles),—so it may occasionally happen that a mule shall breed from the circumstance of its being "a monster respecting mules."
The doctrine of equivocal generation has received no support from any recent investigations. All that is known decidedly leads to the opposite conclusion; and if certain mysterious or unaccountable phenomena have perplexed the physiologist, the only legitimate deduction is, that he has met with something which he cannot comprehend; for those aberrations (if such they really are) from the usual laws of nature are not so much exceptions to the general rule, as additional instances of effects in nature, the regulating causes of which we are as yet incapable of demonstrating. The rules of philosophizing lead us to reject the admission of more causes than are sufficient for the explanation of phenomena; and if, for example, mites, and "such small deer," derived their origin solely from the caseous and other substances in which they are generally found, the sexual distinctions which prevail among other animals would in them be unnecessary, and would not therefore be observable. But we know that distinct sexes do exist among these minute creatures—that they propagate their kinds after the accustomed mode—and we hence fairly infer that fortuitous generation does not take place among them. May we not therefore conclude that the origin of those first observed is similar to that of the thousands which we afterwards see produced according to the usual process? Nature does nothing in vain, and it is not consonant with her usual practice to suppose that she would authorize two distinct modes of creation in the same animal, where one of these is evidently perfect and self-sufficient. It may therefore be laid down as a general rule, that all living beings proceed from others of a similar nature, either by generation, offset, or some other means; and that, in all instances of apparently spontaneous pro-
duction, there has existed some minute or imperceptible germs, which deceive us by their sudden development when placed under favourable circumstances. "In fact," says Cuvier, "however feeble and minute the parts of an embryo or the seed of a plant may be at the moment we are first capable of perceiving them, they then enjoy a real life, and possess the germ of all the phenomena which that life may afterwards develop. These observations, extended to all the classes of living bodies, lead to this general fact, that there are none of those bodies which have not heretofore formed part of a body similar to itself, from which it has been detached." "It is from them (their parents) they have received the vital impulse; and hence it is evident that, in the actual state of things, life proceeds only from life, and that there exists no other, except that which has been transmitted from one living body to another by an uninterrupted succession." "Origin by generation, growth by nutrition, termination by death, are the general and common characteristics of all organized beings."
At the same time it must be admitted, that the origin of many infusory and intestinal animals is sufficiently obscure. Of the latter class, one of the most extraordinary is a monstrous worm, as it may be called, which at distant intervals, and in parts of the world far removed from each other, has been found to inhabit the liver of the human race. The means by which it is bred, or the circumstances favourable to its production, are quite unknown; and some of the most philosophical inquirers of the present day have been unable to account for its origin, otherwise than by supposing that the viscus called the liver becomes, under certain circumstances, endowed with the power of actually secreting a substance capable of assuming and presenting the phenomena of distinct animal existence, and which, prior to the period of its being observed, had in fact become a specific animal;—at least its existence, unlike that of mites, flies, &c. which so often misled the ancient naturalists (though "in limo non ex limo" is Ovid's more accurate expression), cannot be accounted for in any other way. "There are," Mr W. S. Macleay observes, in his excellent and ingenious Horæ Entomologicae, "many circumstances which might be adduced to support the belief that, whether from disease or other causes, there are periods when other parts of a body besides the ovary may produce living germs, and demonstrate thus the polype nature of the cellular substance."
A polypus has been sometimes described as an animalized tube, capable of digestion, and possessed of a certain power of motion and reproduction; and these few words may be said to contain almost all that we know of its essential nature and attributes. As we advance in the scale of creation, we find a more complicated system of organs, with more varied powers of action, and a higher development of those accommodating instincts which, though circumscribed within certain impassable boundaries, yet seem at times to form such an approach to reason, as to connect the unvarying mechanical actions of the most simple zoophysical tribes with the conscious self-regulating power which has its final and most perfect development in the human race. The excellence of man, however, physically considered, consists more in the balance of various powers than in any one bodily superiority; for there is in fact no single sense in which he is not excelled by one or other of the brute creation. Materialists, who regard the intellectual superiority of man as the result of his physical structure, must also, for the sake of consistency, maintain his excellence as a machine to be infinitely be-
Animal Kingdom. fore that of every other animal. But as his indubitable superiority depends on something totally immaterial, which "throws him out of the group of animals, and makes him an insulated being," there is the less necessity for either naturalists or metaphysical inquirers endeavouring to demonstrate the superexcellence of his physical condition. Man is in all cases "wonderfully," and in many cases "fearfully made;" but in the powers of sight, touch, hearing, and smell, he is greatly surpassed by many animals; and even in the sense of taste, in which his practice is more varied and extensive, he is at least equalled by the great majority. It is indeed somewhat remarkable that the last-named sense, the only one in regard to which the human race can lay claim to the possession of equal excellence with the brutes that perish, should be the grossest and least intellectual of the whole.
Although it is by no means strictly true that the brain, considered in relation to the size of the body, decreases as we descend from man to the lower tribes, because in many small birds, such as sparrows and finches, the brain is relatively much larger than in the human race, yet, exclusive of some such exceptions, it may be asserted that that important organ becomes less as we descend from mammiferous animals and birds, to reptiles, fishes, and other lower forms. Yet no very accurate conclusion can be deduced regarding the degrees of intelligence in different animals, from the proportion which the quantity of brain bears to the mass of the whole body, particularly when we come to compare animals of the same class with each other. It is in fact by no means easy to ascertain with accuracy what that proportion really is, because the weight of the brain is supposed to remain the same, while that of the animal varies according to its temporary condition. In this way only can we account for the contradictions which appear in the tabular views which have been given of these proportions by physiologists. Upon the whole, the smaller animals pertaining to the higher classes appear to have proportionally the largest brain, though man is in this respect seldom surpassed. The proportional weight of the brain to the body of man varies from 1-22d to 1-35th part, that of the gibbon or long-armed ape is as 1 to 40, that of the young marmoset (Simia Fauna) as 1 to 24, that of the fox as 1 to 205, that of the beaver as 1 to 290, that of the field-mouse as 1 to 31, that of the elephant as 1 to 500, that of the horse as 1 to 400, that of the eagle as 1 to 160, that of the sparrow as 1 to 25, that of the canary-bird as 1 to 14, that of the cock as 1 to 25, that of the goose as 1 to 360, that of the land-tortoise as 1 to 2240, and that of the sea-tortoise as 1 to 5688.
Soemmering, Ebell, Vicq-d'Azir, Gall, and Tiedemann, supposed that every thing depended on the volume of the brain. But as Buffon and Daubenton had proved that the Sapajous have the brain proportionally larger than man, without surpassing their congeners in intelligence, it has been maintained by others that the volume alone was not a condition of superiority. Now the Sapajous in question have no convolutions to the brain, so that the surface of that organ is represented by that of the interior of the cranium; and exceeds it in other cases in proportion as its folds are numerous and profound; and as there appears to be a constant relation among mammiferous animals between the diminution of the cerebral surfaces and their intellectual degradation, whilst no such relation can be traced between the degrees of degradation and the variations of the brain in respect to size, it has hence been inferred by some that the extent of surface, and not the volume of
the brain, ought to be regarded as co-relative with the intellectual faculties.1
Animal Kingdom. In proportion, however, as the superior portion called the brain decreases in size, the medullary matter appears to collect in other parts of the body, or in the cords which emanate from the brain; so that many animals with much smaller brains have nerves more voluminous in proportion to their bodies than those of man. This medullary substance, the medium of sensation, is, in the human race especially, collected into one principal mass as the engine of thought and reflection, the intellectual attributes by which man is characterized; but it becomes dispersed in the inferior animals, or ramified over the whole body in the form of ganglions or nervous chords, without any preponderating superior brain. It is owing to this dispersion of the nervous system into these small separate centres in the polypus and other tribes, that almost every portion of the body, when separated from the rest, is capable of becoming a distinct animal, and of assuming an independent existence. In the lowest tribes of all, in which the nervous system has not yet been demonstrated, it probably consists of molecules of inconceivable minuteness, disseminated through the pulpy or gelatinous masses of which the bodies of many radiated and infusory animals are composed.
Singular effects result from the dispersion of the brain into so many small and separate centres; and this class of phenomena also illustrates the analogy which exists between the lower animals and the vegetable world. Among the superior creatures no reproduction takes place except of the fluids, and of whatever partakes of the nature of the epidermis. Injury is repaired and superficial parts renewed, but nothing resembling regeneration of important organs ever takes place. But it is otherwise with the inferior orders. The tentacula of the polypus and of many molluscos animals, the rays of the star-fish, the external members of the salamander, and the entire head, with the eyes and antennæ of the snail, when cut off, are speedily renewed. There are also animals, such as the planaria, which reproduce by offsets after the manner of plants; and a polypus may be divided into many portions, each of which becomes perfect according to its kind;—thus in a manner realizing what the ancient poets have feigned regarding the hydra of the Lernean marshes.
If the head of a mammiferous quadruped, or of a bird, is cut off, the consequences are of course fatal. But the most dreadful wounds that imagination can figure or cruelty inflict have scarcely any destructive influence on the vital functions of many of the inferior creatures. Riboud stuck different beetles through with pins, and cut and lacerated others in the severest manner, without greatly accelerating death. Leeuwenhoek had a mite which lived eleven weeks transfixed on a point for microscopical investigation. Vaillant caught a locust at the Cape of Good Hope, and after excavating the intestines, he filled the abdomen with cotton, and stuck a stout pin through the thorax, yet the feet and antennæ were in full play after the lapse of five months. In the beginning of November, Redi opened the skull of a land-tortoise, and removed the entire brain. A fleshy integument was observed to form over the opening, and the animal lived for six months. Spalanzani cut the heart out of three newts, which immediately took to flight, leapt, swam, and executed their usual functions for 48 hours. M. Virey informs us, "Nous avons vu une salamandre vivant depuis deux mois, quoique décapitée au moyen d'une ligature serrée du cou." A decapitated beetle will advance over a table, and recognise
1 See Desmoulins, Rech. Anat. et Phys., and the Journ. Compt. du Dict. des Sciences Méd. Septembre 1822.
animal a precipice on approaching the edge. Redi cut off the Kingdom-head of a tortoise, which survived 18 days. Colonel Pringle decapitated several libellulæ or dragonflies, one of which afterwards lived for four months, and another for six; and, which seems rather odd, he could never keep alive those with their heads on above a few days.1
Some curious particulars connected with the great tenacity of life in the lower animals are mentioned by Mr Fothergill.2 A friend being employed one day in the pursuit of insects, caught a large yellow dragonfly (Libellula varia), and had actually fastened it down in his insect box, by thrusting a pin through the thorax, before he perceived that the voracious creature held a small fly, which still struggled for liberty, in its jaws. The dragonfly continued devouring its victim with great deliberation, and without expressing either pain or constraint, and seemed totally unconscious of being pinned down to the cork, till its prey was devoured, after which it made several desperate efforts to regain its liberty. A common flesh-fly was then presented to it, when it immediately became quiet, and ate the fly with greediness: when its repast was over it renewed its efforts to escape. This fact being mentioned to Mr Haworth, the well-known English entomologist, he confirmed the truth of the remarkable insensibility to pain manifested by insects, by narrating an additional circumstance. Being in a garden with a friend who firmly believed in the delicate susceptibility of these creatures, he struck down a large dragonfly, and in so doing unfortunately severed its long abdomen from the rest of the body. He caught a small fly, which he presented to the mutilated insect, by which it was instantly seized and devoured; and a second was treated in the same manner. Mr Haworth then contrived to form a false abdomen, by means of a slender portion of a geranium; and after this operation was performed the dragonfly devoured another small insect as greedily as before. When set at liberty, it flew away with as much apparent glee as if it had received no injury. It is a fact well known to practical entomologists, that large moths found asleep during the daytime may be pinned to the trunks of trees without their appearing to suffer such a degree of pain as even to awake them. It is only on the approach of the evening twilight that they seek to free themselves from what they must no doubt regard as an inconvenient situation.
The cruelty of zoological, especially of entomological pursuits, has too often been stated as an objection to the practical parts of the study of natural history. When a noble aristocrat (who thinks it sport to shoot a shepherd's dog) slaughters 100 brace of grouse in a single day, we hear nothing of such an objection, possibly because the flavour of moor-game is very exquisite; and the reason of defence is good. But the tastes of men differ, and fortunately, as all have not the means of an equal gratification from the same source. "Cruelty," say Messrs Kirby and Spence, "is an unnecessary infliction of suffering, when a person is fond of torturing or destroying God's creatures from mere wantonness, with no useful end in view; or when, if their death be useful and lawful, he has recourse to circuitous modes of killing them, where direct ones would answer equally well. This is cruelty, and this with you we abominate; but not the infliction of death when a just occasion calls for it. They who see no cruelty in the sports of the field, as they are called, can never, of course, consistently allege such a charge against the entomologist; the tortures of wounded birds, of fish that swallow the hook and break the line, or of the hunted hare, being beyond comparison greater than those of in-
sects destroyed in the usual mode. With respect to utility, the sportsman, who, though he adds indeed to the general stock of food, makes amusement his primary object, must surely yield the palm to the entomologist, who adds to the general stock of mental food, often supplies hints for useful improvement in the arts and sciences, and the objects of whose pursuit, unlike that of the former, are preserved, and may be applied to use for many years. But in the view of those even who think inhumanity chargeable upon the sportsman, it will be easy to place considerations which may secure the entomologist from such reproof. It is well known, that in proportion as we descend in the scale of being, the sensibility of the objects that constitute it diminishes. The tortoise walks about after losing its head; and the polypus, so far from being injured by the application of the knife, thereby acquires an extension of existence. Insensibility almost equally great may be found in the insect world. This, indeed, might be inferred a priori, since providence seems to have been more prodigal of insect life than of that of any other order of creatures, animalcula perhaps alone excepted. No part of the creation is exposed to the attack of so many enemies, or subject to so many disasters; so that the few individuals of each kind which enrich the valued museum of the entomologist, many of which are dearer to him than gold or gems, are snatched from the ravenous maw of some bird or fish, or rapacious insect, would have been driven by the winds into the waters and drowned, or trodden under foot by man or beasts; for it is not easy in some parts of the year to set foot to the ground without crushing these minute animals; and thus also, instead of being buried in oblivion, they have a kind of immortality conferred upon them. Can it be believed that the beneficent Creator, whose tender mercies are over all his works, would expose these helpless beings to such innumerable enemies and injuries, were they endowed with the same sense of pain and irritability of nerve with the higher orders of animals?"3 Instead, therefore, of believing, and being grieved by the belief, that the insect we tread upon,
In corporal sufferance finds a pang as great
As when a giant dies,
the very converse is nearer the truth. "Had a giant lost an arm or a leg," continue the authors just quoted, "or were a sword or spear run through his body, he would feel no great inclination for running about, dancing, or eating. Yet a tipula will leave half its legs in the hands of an unlucky boy who has endeavoured to catch it, and will fly here and there with as much agility and unconcern as if nothing had happened to it; and an insect impaled upon a pin will often devour its prey with as much avidity as when at liberty. Were a giant eviscerated, his body divided in the middle, or his head cut off, it would be all over with him; he would move no more; he would be dead to the calls of hunger, or the emotions of fear, anger, or love. Not so our insects: I have seen the common cockchafer walk about with apparent indifference after some bird had nearly emptied its body of its viscera; a humble bee will eat honey with greediness though deprived of its abdomen; and I myself lately saw an ant, which had been brought out of the nest by its comrades, walk when deprived of its head. The head of a wasp will attempt to bite after it is separated from the rest of the body; and the abdomen, under similar circumstances, if the finger be moved to it, will attempt to sting." Query, which part felt conscious of being the original wasp?
That the acuteness of bodily suffering, even among the
1 See the observations prefixed to the translation of Spallanzani's Tracts, by John Graham Dalyell, Esq.
2 Essay on Natural History.
3 Introduction to Entomology, vol. i. p. 56.
higher classes of the brute creation, is in some manner providentially subdued, and rendered so much less acute as not to be a fit subject of comparison with the suffering of the human race, is indeed evident from various phenomena, whatever the cause may be. The writer of this article has seen a turtle-dove (Columba risoria) which was so severely lacerated by a cat, that the contents of its stomach were torn out. The painfully excited sympathy of those who had long cherished the gentle creature was, however, in a great measure allayed by seeing the bird immediately afterwards proceed to pick up the fresh grains of barley which (till the aid of the surgeon was called in) continued to fall from its wounded paunch.
Considerations of the nature glanced at in the preceding paragraphs can never, of course, be so misconstrued as to afford any palliation to wanton or inconsiderate cruelty to the brute creation. The judges of the Areopagus who condemned to death the child whose amusement it had been to pluck out the eyes of quails, were regulated in their determination by the motives imputed to the young criminal, and which they deemed expressive of so cruel and pernicious a character, that in after-times he would assuredly offend the state. "Nec mihi videntur Areopagitæ," says Quintilian, "cum damnaverunt puerum coturnicum oculos eruentem, aliud iudicasse, quam id signum esse perniciosissime mentis, multisque malo future, si adolevisset."1 But had some great oculist, intent on the structure and physiology of the human eye, and engaged in a difficult course of experimental observation, by means of which the "dim suffusion" which often veils the orbs of his fellow-men might be obviated or decreased, found himself under the necessity of having recourse to a somewhat similar operation, the case would have assumed another character, and the most sentimental philanthropist must have applauded the practice of the philosopher. So it is in a great measure with the pursuits of the naturalist. If the wonderful structure of the lower orders of creation cannot be studied or understood, or their infinitely varied forms held in remembrance, without hastening by a few days or hours the termination of that brief career which in truth scarcely ever meets with a strictly natural end, then is the student of nature, following out the principles of an elevating and intellectual pursuit, as well entitled to command a portion of animal life as he who, to pamper the refined grossness of a sensual appetite, bleeds his turkeys to death by cutting the roots of their tongues, boils crabs and lobsters alive, and swallows unsuspecting oysters by the score.
The more perfect the nervous system, the greater is the degree of intelligence. Indeed, were it not that no trace of that system has yet been discovered in many zoophytes, we might almost assert that the presence of nerves constitutes animal life, and that their absence in organized matter reduces it to the vegetable state. The greater the extent of brain in proportion to the size of the body, the greater in general the degree of sensibility. A French anatomist, in dissecting a horse of which he had admired the noble qualities, exclaimed, "J'ai long temps douté si nous avions le droit de monter sur ton dos; mais en voyant la petite capacité de ton cerveau, je n'en doute plus maintenant; tu n'est qu'une bête." The most perfect animals are such as are provided with a head which serves as the centre of their sentiments and sensations, and with a mouth for the reception of their nourishment. Their forms are symmetrical, or composed of two equal parts; they
change their place by a voluntary act; their sexes are distinct, and separately incapable of continuing the species; they are provided with five senses, and endowed with the perception of pleasure and of pain. The inferior tribes, on the contrary, which present so many analogies to the vegetable kingdom, have no distinct head, or single organ of life; they are not symmetrical or composed exactly of two equal parts, but rather affect the circular or radiated form; and for the most part they either remain fixed to the place which gave them birth, or with difficulty change their places of abode. The sexes are frequently united in the same individual, and their senses are limited to such as are necessary to a very confined and almost vegetative existence.
Though no animal has more than five senses, a great many are much more sparingly endowed. The only universal sense seems that of touch. The next to be developed is probably that of taste, then sight, hearing, and, lastly, smell. In the human race the senses are more equally balanced than in the brute creation, among the different tribes of which we find many animals as remarkable for their extreme acuteness in certain senses, as for their obtuseness in respect to others. The sense of smell in the dog, excepting some artificial varieties, such as the greyhound, prevails over every other; birds of prey are remarkable for their keenness of sight; the sense of hearing is strong in the hare; that of touch in the trunk of the elephant; that of taste in the lord of the creation. It follows as a consequence that the dog is by nature a hunting animal; that the eagle, upborne upon resplendent wing, describes its magnificent circles in the air, "sagacious of its quarry from afar;" that the hare couches securely among the long dewy grass, with its head so low that its eyes must be almost useless, but trusting to its quicker ears, which warn it of an approaching foe; that the elephant examines the exact nature of all objects by touching them with the fleshy finger of its proboscis; and that Mrs Rundell's work on cookery has run through countless editions. All insects in the perfect state, and the greater proportion of their larvæ, a part only of the molluscan tribes (such as the inhabitants of univalve shells), crustaceous animals, such as crabs and lobsters, and all fishes, reptiles, birds, and quadrupeds, enjoy the sense of sight; and all these classes (with the exception of insects and many of the mollusca) are also furnished with the organs of hearing. That the latter sense, however, also exists in insects, may be fairly inferred from the frequent and varied sounds which they are capable of producing, although the seat of the faculty has not yet been ascertained. Many zoophysical tribes, which have no special organs of sight, appear to become sensible to the presence and action of light, through a delicate perception of the sense of touch. According to Buffon, the sense which has the strongest affinity to thought is that of touch; and he regards it as being enjoyed by man in greater perfection than by animals. That which has the strongest affinity to instinct and appetite is smell,—a sense in which man must acknowledge an infinite inferiority. Hence, according to the Frenchman, man has the greatest tendency to knowledge, and the brute to appetite. There is no doubt that in man and the different species of monkeys the sense of touch is highly discriminating; but it is assuredly a false view of the subject which has led Helvetius and others to attach such an extraordinary degree of importance to the hand, as the medium of intellectual superiority in the human race.
Whatever exhibits the phenomena of either animal or
1 De Inst. Orat. lib. v. cap. ix. de Signis.
Animal Kingdom. vegetable life, advances towards the perfect development of its parts through the medium of aliment. This name is applied to the numerous and diversified substances which, when introduced into the system of an organized body, have the power of identifying themselves in part with that system, in such a manner as to effect its nourishment, reparation, and increase. "Nourishment," says Bacon, "ought to be of an inferior nature and more simple substance than the thing nourished. Plants are nourished with the earth and water, living creatures with plants, man with living creatures. There are also certain creatures feeding upon flesh; and man himself takes plants into a part of his nourishment: but man and creatures feeding upon flesh are scarcely nourished with plants alone. Perhaps fruits or graines, baked or boyled, may with long use nourish them, but leaves of plants or herbs will not do it; as the order of the Foliataes showed by experience living creatures are nourished by the mouth; plants by the root; young ones in the womb by the navil; birds for a while are nourished with the yolke in the egge, whereof some is found in their crops after they are hatched. All nourishment moveth from the centre to the circumference, or from the inward to the outward: yet it is to be noted, that in trees and plants the nourishment passeth rather by the barke and outward parts than by the pith and inward parts; for if the barke be pilled off, though but for a small breadth round, they live no more: and the blood in the veins of living creatures doth no lesse nourish the flesh beneath it than the flesh above it. Vegetables assimilate their nourishment simply without excreting; for gums and teares of trees are rather exuberances than excrements; and knots or knobs are nothing but diseases. But the substance of living creatures is more perceptible of the like; and therefore it is conjoyned with a kinde of disdain, whereby it rejecteth the bad and assimilateth the good. It is a strange thing of the stalkes of fruits, that all the nourishment which produceth sometimes such great fruits should be forced to passe thorow so narrow necks, for the fruit is never joyn'd to the stock without some stalkes. It is to be noted, that the seeds of living creatures will not be fruitful but when they are new; but the seeds of plants will be fruitful a long time after they are gathered; yet the slips or cions of trees will not grow unless they be grafted green, neither will the roots keepe long fresh unless they be covered with earth."
Nutritive substances of course vary according to the nature of the bodies which consume or absorb them. Plants derive their chief nourishment from air and water, the former of which must contain carbonic acid gas, the latter the dissolved remains of animal or vegetable substances. It is, however, possible to produce vegetable growth from pure water, assisted by warmth and air. Vegetables, again, serve as food to the greater proportion of animals, and these in their turn are devoured by the carnivorous few. It is thus that the productions of nature are connected together in one great circle, and are reciprocally dependent on each other. Without water there could be neither plants nor herbivorous animals, and without herbivorous animals there could be no carnivorous ones; therefore, without water there could be no life. Inorganic matter furnishes the first and most simple materials of existence; organic bodies perish and become decomposed, and thus adding to the mass of inorganic matter which they had for a short period abandoned, they enter again as elements into the composition of other and more complex forms. Indeed, according to Mr W. S. Macleay, organized matter is nothing but a pecu-
liar modification of brute matter acted upon by the vital principle; but this form of expression probably throws no new light upon the subject.
We may here present a remark not unworthy of attention regarding the nature of the flesh in the different classes of the animal kingdom. Considered as a viand, the flesh of animals becomes less substantially nourishing as we descend in the scale. For example, the flesh of a quadruped contains a greater quantity of nourishment in proportion to size and weight than that of a bird, while the latter exceeds in that respect both reptiles and fishes. Hence in catholic countries the latter are justly regarded as meagre, and form an exclusive food during the frequent days of abstinence by which it is sought to mortify the flesh. Shell-fish and crustacea, and a fortiori the zoophytical tribes, yield a still smaller proportion of nutritious matter. A revolting conclusion has been drawn from this alleged relation between the flesh of a highly organized animal and the power and excellence of its nutritive qualities; viz. that cannibalism, or the habit of anthropophagous nations, opens up to those unnatural tribes a pleasure connected with the indulgence of the sense of taste greatly surpassing what is enjoyed by those who confine their mastication to the brute creation; because, in accordance with the rule supposed, the organic perfection and highly animalized nature of man is productive of a higher degree of nutrition, and of a greater capability of direct assimilation, when the substance of which he is composed is used as food by his fellow-mortals. But the scale of alimentary substances may rather be said to commence with air and water, and to terminate with the herbivorous animals; for the flesh of carnivorous kinds is, with very few exceptions, of a nature inadequate to the healthy sustenance of life. It is of a quality too putrescent, and decomposes with too great rapidity, as if the organization of matter could make no further progress, but passing rapidly from one extreme to another, hastened to throw off even the semblance of life, to assume again the simplest elementary form. "Over-great affinity," says Bacon, "or consubstantiality of the nourishment to the thing nourished, proveth not well; for creatures feeding upon herbs touch no flesh; and of creatures feeding upon flesh few of them eat their owne kinde. As for men which are cannibals, they feed not ordinarily upon men's flesh, but reserve it as a dainty either to serve their revenge upon their enemies, or to satisfy their appetite at some times. So the ground is best sowne with seed growing elsewhere; and men do not use to graft or inoculate upon the same stocke."
Mineral bodies are still more unfit for the purposes of nutrition. They furnish both medicines and poisons in abundance, but never aliments. The difference between these objects may be shortly stated as follows: Aliments are substances alterable by the action of the organs which appropriate them; medicines act on the organs, of which they alter or modify the action; poisons attack and extinguish life itself. But according to the specific nature of different animals, and various other circumstances, the qualities of these agents are convertible, so that aliments become poisonous, and poisons alimentary. Thus opium, which among European nations is a medicine, and too frequently a poison, has become, according to the practice of several eastern nations, an alimentary substance. Aloes, which are simply medicinal for the human race, are a destructive poison to many carnivorous animals. On the other hand, according to Pallas, hedgehogs eat abundantly of cantharides without being in the slightest degree incommoded by them; and bees are known to feed
Animal Kingdom. upon and form their honey from the secretions of many pernicious and even poisonous plants. The caterpillar of a certain sphinx moth is highly delighted with the acrid and venomous fluid of a tithymalis.
The more that animals enjoy the qualities of youth, strength, and activity, the greater is the increase and development of their parts, and the greater the necessity for an abundant supply of food. Of many individuals exposed to an absolute abstinence of many days, the young are always the first to perish. Of this the history of war and shipwreck offers in all ages too many frightful examples. There are several instances on record of an almost total abstinence from food for an extraordinary length of time. Captain Bligh, of the Bounty, sailed nearly 4000 miles in an open boat, with occasionally a single small bird not many ounces in weight for the daily sustenance of 17 people; and it is even alleged, that 14 men and women of the Juno, having suffered shipwreck on the coast of Arracan, lived 23 days without any food. Two people first died of want on the fifth day. In the opinion of Rhedi, animals support want much longer than is generally believed. A civet cat lived 10 days without food, an antelope 20, and a very large wild cat also 20; an eagle survived 28 days, a badger one month, and several dogs 36 days. In the memoirs of the Academy of Sciences there is an account of a bitch, which having been accidentally shut up alone in a country-house, existed for 40 days without any other nourishment than the stuff on the wool of a mattress which she had torn to pieces. A crocodile will live two months without food, a scorpion three, a bear six, a chameleon eight, and a viper ten. Vaillant had a spider that lived nearly a year without food, and was so far from being weakened by abstinence, that it immediately killed another large spider, equally vigorous but not so hungry, which was put in along with it. John Hunter inclosed a toad between two stone flower-pots, and found it as lively as ever after 14 months. Land-tortoises have lived without food for 18 months; and Baker is known to have kept a beetle in a state of total abstinence for three years. It afterwards made its escape.1 Dr Shaw gives an account of two serpents which lived in a bottle without any food for five years.
The necessity of aliment becomes less vividly felt during sleep, and certain other periods of prolonged repose. There are several animals which hibernate, or go into winter quarters for six months in the year, during which period many of them require no food, but are maintained solely by that excellence of bodily condition which they had acquired during a prior period of activity and good cheer. This leads us naturally to consider what is called the hibernation of animals.
Many creatures are so constituted that the activity of their functions is greatly impaired by a comparatively slight reduction of temperature. Naturalists and anatomists have alike sought in vain for either external or internal characters of general application, by which they might distinguish, a priori, the species subjected to this strange though well-ordered lethargy. They belong to various genera and tribes, many of which have few characters in common, as will be perceived when we name as well-known instances the dormouse, the hedgehog, and the bat. It influences both warm and cold-blooded animals. The former of these, at certain advanced periods of the autumn, according to the species, seek out places of repose, either in the earth, among old walls, in caverns, trunks of trees, or bushes; which retreats they usually line with dried herbs, grasses, leaves, or moss. The bat chooses caverns, churches, barns, and other situations
where the temperature is milder than that of the open air; and, contrary to the usual practice, it suspends itself by the hooked claws of its hinder extremities. It is the practice of other hibernating animals to contract themselves into a ball, in such a manner as to expose the smallest possible surface to the action of the air. When discovered in their retreats they are generally thus rolled up, cold to the touch, their limbs stiffened, their eyes closed, their respiration slow, interrupted, sometimes even imperceptible, and their insensibility so great that they may be removed, rolled about, and otherwise maltreated, without showing any further signs of life.
It has been observed that the temperature of these animals gradually lowers itself as the season declines. Their respiration also becomes slower, their motions less lively, and their appetite diminishes; but sensation and the power of locomotion still continue. This intermediate state between the perfect performance of the vital functions and confirmed torpidity endures for several weeks; the degree of temperature at which different animals become entirely overpowered varying, of course, according to the species. The propensity has been observed, in the following well-known animals, to correspond to a scale of descending temperature, according to the following order:—1st, The bat; 2dly, the hedgehog; 3dly, the dormouse; 4thly, the marmot; 5thly, the hamster. Although many other animals are subject to the same law, it is only among those just enumerated that an exact comparison has been instituted.
A complete state of hibernation consists in the suspension of sensation and voluntary motion, in addition to a great decrease in the temperature of the body, and in the frequency of respiration. Its different degrees of intensity are well ascertained by the number of respirations in a given time, or, in its most perfect state, by the total suspension of all respiratory movements. The different species of the bat tribe are those of which the torpidity is the least profound; and the marmot probably experiences the greatest degree of vital suspension. The temperature of these animals during their lethargy depends in a great measure upon that of the external air, and is consequently variable. It is in general, however, superior to it by several degrees. It may descend to within a few degrees of the freezing point, but is not susceptible of reduction to that point, without producing either re-action of the vital functions or death. There is, therefore, contrary to the opinion of some of the older naturalists, a degree of external cold incompatible with the torpidity or existence of these animals. The species most easily rendered torpid, such as the bat, the hedgehog, the dormouse, the lerot, and the muscardine, cannot support a cold of 14° of Fahrenheit. A warmth of from 50° to 53° brings them again to life. Sundry mechanical means, such as different degrees of motion, serve to restore several of the last-named species without any increase of temperature; but to preserve them in a state of prolonged activity, a gentle warmth must be applied and continued.
It is evident, from these and other observations, that the sleep of mammiferous animals is not characterized by a uniform and constant duration. As it is dependent on the variations of the atmosphere, it will commence at an earlier, continue a longer, or be interrupted after a shorter period, according to the difference in the seasons of particular years, the skill which the animals may have exhibited in the choice of a protecting habitation, or the peculiar constitution of the species, or even of the individuals. The habit of storing up a supply of winter provisions also depends upon their greater or less degree of exposure to
1 See the observations prefixed to the translation of Spallanzani's Tracts, before referred to.
the power of awakening influences. The hedgehog, for example, has been observed to form several separate magazines, to which it has recourse during the winter season; and the marks of its little feet have sometimes been traced on the surface of the surrounding snow.
The hybernation of the swallow is a point on which very dissimilar opinions have been promulgated. It now appears to be the prevailing belief that these birds migrate on the approach of winter to other and more genial climates, but that cases do occur in which such individuals as are prevented by circumstances from joining the "marshalled array," are enabled to survive the rigours of our northern winters by the power which their constitution possesses of assuming the torpid state; at least the occurrence of torpid swallows, however rare, is too well authenticated to be a matter of doubt.
It is said that the tanrec, a species of hedgehog found in Madagascar, becomes torpid for some months in the year. If this assertion is well founded, it affords the only known instance of torpidity in a mammiferous quadruped of a warm climate.
Many cold-blooded animals may be regarded as of the hybernating kind. Indeed the greater proportion of reptiles, insects, molluscous animals, &c. inhabiting cold countries, are very lethargic during the winter season, which they usually pass without food. They appear subject to the influence of this feeling even in warm climates; at least Humboldt describes certain reptiles in South America which pass a portion of the year buried in the earth, and which are only aroused by the occurrence of rainy weather or the excitement of violent means. "The manners of animals," says this enlightened observer, "vary in the same species, according to local circumstances difficult to investigate. We were shown a hut, or rather a kind of shed, in which our host of Calabo, Don Miguel Cousin, had witnessed a very extraordinary scene. Sleeping with one of his friends on a bench covered with leather, Don Miguel was awakened early in the morning by violent shakes and a horrible noise. Clods of earth were thrown into the middle of the hut. Presently a young crocodile, two or three feet long, issued from under the bed, darted at a dog that lay on the threshold of the door, and, missing him in the impetuosity of his spring, ran toward the beach to attain the river. On examining the spot where the barbacon or bedstead was placed, the cause of this strange adventure was easily discovered. The ground was disturbed to a considerable depth. It was dried mud, that had covered the crocodile in that state of lethargy, or summer sleep, in which many of the species lie, during the absence of the rains, amid the llanos. The noise of men and horses, perhaps the smell of the dog, had awakened the crocodile. The hut being placed at the edge of the pool, and inundated during part of the year, the crocodile had no doubt entered, at the time of the inundation of the savannahs, by the same opening by which Mr Pozo saw it go out. The Indians often find enormous boas, which they call uji, or water-serpents, in the same lethargic state. To re-animate them, they must be irritated, or wetted with water."
Upon the whole, naturalists seem to be of opinion that no species of animal is condemned to torpidity by any inherent property of its nature. It is a provisional faculty, dependent on external circumstances, and may be interrupted, postponed, or altogether prevented, by regulating the conditions under which the animal is placed.
The disposition of animals in relation to other individuals of the same species differs considerably. There are some which unite in couples and divide between them
the cares of the family. This is usually the case among the various tribes of birds, and also among carnivorous quadrupeds; whilst the males of such as feed on vegetables, and which consequently find almost everywhere an abundant and easy nourishment, abandon to the mother the rearing and education of their young. It has also been observed, that among such birds as feed on living prey, the male is very assiduous in assisting his mate to procure a sufficient supply. But naturalists have erred in assigning the polygamous habit as a general characteristic of the gallinaceous kinds. The instinct to pair, or the habit of monogamy, is no doubt only bestowed on those species to which it is necessary for the rearing of their offspring, and differs considerably in the nature and permanence of the attachment, according to the position of the nest, i.e. whether it is built upon or above the surface of the ground. All birds which build on trees, as was long ago remarked by Lord Kames, are hatched blind, and almost without feathers, and consequently require the sedulous care of both parents. But the generality even of gallinaceous birds, which breed upon the ground, do likewise pair, though the hatching of the eggs is entirely confined to the female, who completes her task by leading the young to their proper food, which they are able immediately to pick up for themselves, being active and well feathered from their birth. The male, at the same time, continues to manifest a certain degree of paternal solicitude, by uttering the alarm-note on the approach of birds of prey, or other dangerous foes. Black game and wood-grouse, however, do not appear to pair at all; but in the spring a male bird assembles a certain number of females about him, which afterwards deposit their eggs, and rear their young altogether independent of the male parent. They are therefore polygamous in the proper acceptance of the term. Even among herbivorous quadrupeds pairing is rare, because the female can suckle her young while she herself is feeding; but the monogamous habit probably obtains among most carnivorous quadrupeds, and certainly among all carnivorous birds, because incubation leaves the female no sufficient time to hunt for food,2 and because young birds cannot bear a long fast, and therefore require the assistance of both parents, while unable to provide for themselves. The association or fellowship of birds is either annual or for life; the former bond is the more usual, though eagles, crows, and several other species afford examples of a long-continued attachment.
Many birds assemble in autumn, winter, and early spring, into flocks, but as soon as the pairing season has commenced they again separate into pairs. Others again appear to be more gregarious during the breeding season than at any other period of the year, for example the gannet or soland-goose (P. bassanus); but this arises not so much from a love of fellowship with their kind, as from the accident of there being few places fitted for the purposes of nidification and the rearing of the young.
We have said that pairing is rare among such quadrupeds as feed on grass, because the female can feed herself at the same time that she is suckling her young. The roe-deer, however, among herbivorous quadrupeds, forms an exception to the general rule. On the other hand, there are several carnivorous quadrupeds which do not pair, but the young of which are left entirely dependent on the mother; that is to say, the latter is obliged both to capture her own food and to suckle her offspring.
Among gregarious quadrupeds which usually store up food for winter, pairing is probably necessary to prevent discord, and in this respect beavers are said to resemble those birds which place their nests upon the ground. As
1 Personal Narrative, vol. iv. p. 300.
2 See Kames's Sketcher.
Animal Kingdom. soon as the young are produced, the males abandon their stock of food to their mates, and live at large, but return frequently to visit them while they are suckling their young. Hedgehogs and most of the monkey kind pair. Seals are polygamous, and turtles leave their young to be hatched by the heated sand. Earwigs, spiders, bees, and woodlice (onisci), are amongst the few of the insect tribes which pay any attention either to their eggs or offspring. The young of the greater proportion of animals is produced in spring, when the supply of food is the most abundant, and when the long period which intervenes before the approach of winter enables them to acquire strength to support the rigours of that inclement season.
Though the period of gestation varies considerably in the different quadrupeds which feed on grass, yet the females are regularly delivered in spring, or early in summer, when the herbage is nutritive and abundant. The mare conceives in summer, carries 11 months, and brings forth in May. The same is nearly the case with the cow. The sheep and the goat are usually in season in November; they carry five months, and produce when grass has begun to spring. They love short, close herbage, upon which a horse or cow would barely thrive. The ass is in season about the beginning of summer, but she bears twelve months, and consequently brings forth likewise early in summer. Wolves and foxes copulate in December, but as they only bear five months, they bring forth in April, when the season has assumed a genial aspect, and animal food is as abundant as at any other season. If we were to guess what would probably be the rutting season of animals, we would say summer, especially in a northern country; and yet, to quadrupeds which carry their young only for four or five months, such economy would be injurious and improvident, as it would bring the time of delivery at an undue season, both for warmth and food.1 There are a few exceptions to the above rule, which, however, in themselves, belong to an equally beautiful system of providential ordinances. Some gregarious and store-collecting animals, for example, bring forth in January, when their granary of provisions is still abundantly filled.
The season of pairing, or of production, among wild animals, usually takes place only once a year, and at a fixed period; but those which man has rendered domestic are observed to couple at all seasons. The species of warmer climates, when transported into colder regions, usually cease to pair, or at least their union is unproductive; and the same consequence generally follows a state of captivity. Among such species, however, as man has fairly reduced to a state of satisfied domestication, the individuals become much more prolific than in the wild state.
The season of love varies greatly among mammiferous animals. The greater proportion pair in spring and summer; but the wolf pairs in winter, the stag in autumn, and many domesticated animals at diversified periods throughout the year. Prolific union takes place among varieties of the same species; and it is by paying attention to these that the finer races of our domestic animals are maintained and continued. As the climate of northern countries causes several of our most valuable animals to degenerate (as it is called), it has been customary to obtain from time to time a male animal of a pure and noble race, which, when paired with an ordinary female, produces a breed scarcely inferior to the male parent; for it has been observed that, with few exceptions, the new produce assumes the characteristics of the father. Thus, in uniting a sheep of an ordinary kind with a ram of the Merino race, the first generation almost equals the father in beauty.
What is frequently called deterioration in animals is,
more properly speaking, their natural assumption of those peculiar attributes which fit them for the inclemencies of climates ungenial to their original nature. Animal Kingdom. A Laplander is no more a deteriorated Asiatic of the Mongolian or Caucasian line, than a Georgian or Circassian is a highly refined Laplander; neither is the Shetland pony a deteriorated Arabian courser, any more than the steed of Araby is a thorough-bred shelly. Each has been enabled by a wise provision of nature to assimilate its character and constitution to the qualities of the climate in which it was destined to exist; and had it been incompetent to effect or undergo such assimilation, it would then indeed have deteriorated—that is to say, it would have died. If we admire the slim smooth elegance of the Italian greyhound, and regard the rough shaggy coat of the dog of Nova-Zembla as a deterioration, let us remember that that which is the beauty of the one would be the bane of the other; and what would then become of that forlorn agriculturist, whose business it is to drill the ice and to furrow the snow? The small stature and peculiar habits of the northern pony would have been as little fitted to sustain the fiery breath or the shifting sands of an eastern desert, as the graceful Arabian to withstand the cold and cloudy climate, and the rugged and precipitous mountains, of Lapland or Thule. Therefore, instead of being deteriorated, each ought rather to be said to exist in the best and most improved condition, according to the nature of its particular calling. Using the word, however, in its more usual acceptation, it may be stated that an animal seldom degenerates in its native country, but more frequently in those for the climate of which its constitution is not adapted. Each species appears to have a certain extent or circle of natural distribution, in the centre of which it not only most abounds, but also there shows itself in its finest and most characteristic proportions. As the places of its occurrence diverge from this centre of dominion, it becomes rarer, and exhibits a variation or considerable departure, at least in its external characters, from the primitive model. Thus the horses of Arabia and Barbary degenerate in Britain; and, to preserve the breed in purity, they must be frequently crossed by the original; but the Arabs themselves are very careful to prevent any mixture in the blood of their native and noble kinds, and would deem them deteriorated by such alliance.
In the tabular or abridged views of classification which we here present, it is our intention merely to exhibit the great primary divisions of the animal kingdom called classes. The secondary divisions into orders, and the further dismemberment of these into minor groups called families, genera, &c., will be illustrated when we come to treat of each class in particular under its proper head. Neither do we intend to trace the progress of classification from the earliest ages of scientific record; because, as the object of the naturalist is rather to ascertain the nature and relationship of things as they are, than as they were supposed to be, there is the less necessity for leaving our direct route, to trace either the origin or the progress of error. We shall proceed, after a few observations, at once to the system of Linnaeus, which is in fact the basis of all that have succeeded, and without a knowledge of which it is impossible to understand either the merits or defects of more recent systems. Indeed, with the exception of the purely artificial classification of Klein, and the multiplied orders of Brisson and Vicq-d'Azir, all the systems which have appeared since the middle of last century are indebted more or less to the labours of the immortal Swede, and may be valued almost exactly in pro-
1 Kames's Sketches.
Animal Kingdom. portion to their share in the lucidus ordo of the Linnaean system. For example, the Systema Regni Animalis of Erxleben (1777) is nothing more than a revised edition of the Systema Naturæ, in which are engrafted, with no lack of skill, many additions both of species and genera; the whole being presented in a consecutive series, without the accustomed subdivision into the primary groups called orders. The Prodromus Methodi Animalium of Storr (1780) does not differ radically from the Linnaean system. The Elenchus Animalium of Bodaert (1787) is allied to it still more closely in every thing except its accuracy. Of Gmelin's work (1789) we need not speak, as it is a professed revision (being the 13th) of the Systema Naturæ. And although no one will deny the merit of profound and original inquiry to the investigations of Blumenbach, most readily will those who are best acquainted with his labours admit, that in zoology he has wisely followed the footsteps of Linnaeus. The six classes into which the German naturalist divides the animated creation, viz. Mammalia, Aves, Amphibia, Pisces, Insecta, and Vermes, correspond with those of the Linnaean arrangement, although their orders and genera are in some respects differently combined. His motto appears to have been Multa fiunt eadem, sed aliter. (Quintilian.)
The signal benefits conferred on natural history, in all its branches, by the learning and genius of Baron Cuvier, are known wherever the science has obtained a zealous and successful cultivator; and it cannot have escaped the notice of the critical observer, that after 30 years of profound and philosophical research into the mysteries of the animal kingdom, the most enlightened zoologist of the age should have finally reverted to a closer approximation to the Linnaean system, than had characterized his views at any former period of his brilliant career. When he first made known (in 1797), conjointly with M. Geoffroy, his new classification of mammiferous animals, his numerous genera were contained under no less than 14 different orders. Thirty years afterwards (in 1817) he published his Règne Animal, with many improvements in the composition and arrangement of the minor divisions, and with the addition of the order of which he is himself so bright an ornament, but otherwise composed (we speak at present of the mammalia alone) of primary divisions exactly the same in number, and nearly the same in nature, as those finally divulged and established by Linnaeus himself just 60 years before.
Latreille, Dumeril, Desmarest, and Frederick Cuvier, are followers or condutors of the Baron, and with him are partakers in the modification and amendment of the Linnaean system. The venerable Lamarck has greatly signified himself in a field which, it must be confessed, was obscure to the eye of Linnaeus—that of the molluscous animals—which, under the name of Vermes Testacea, were but indifferently treated in the Systema Naturæ. The error appears to have lain in the greater attention which was bestowed on the shells themselves, or testaceous coverings, than on the animal inhabitants; and the consequence has been, that the conchologist of the old school ranks with the collector of china, whether old or new.
The names above enumerated are certainly among the foremost in the annals of modern science; and although, in addition to these, many more might be mentioned with honour as having contributed, by monographs or other partial though highly prized contributions, to the increase of knowledge, yet we are not aware that more than three systematists of acknowledged and wide-spread influence, or of what may be termed universal celebrity, remain unnoticed, of those who have essentially influenced the present condition of zoological science; we mean Fabricius, Illiger, and M. de Blainville. We have no hesita-
tion in asserting, that as the writers first mentioned owe much of the success which has attended their labours to their having judiciously engrafted their own improvements on the original stock of the Linnaean system, so the authors last named, though not less highly gifted, have in a great measure sacrificed the utility of many original and enlightened views to the fond conceit of a new, and in some instances an incomprehensible, nomenclature.
The skill of Fabricius as an entomologist has never been surpassed, and it is therefore the more to be regretted that he should have been influenced in the formation of his system by other motives than a desire to perceive and point out the truth. But it is known that he was swayed as much by the ambitious hope of founding a new doctrine, of which he destined himself to be the oracle, as by the desire of proceeding directly in the path of nature. Hence his avowed enmity to the eclectic system of Latreille, which, during the opening career of that celebrated entomologist, he declared it to be his intention utterly to destroy. Yet the system of Latreille not only stands, but, when viewed in relation to the application of its general principles, has in a great measure superseded that of Fabricius. At the same time, the accurate discrimination and extensive knowledge of the latter, and the wide circle which his system embraces in detail, render it still indispensable for a knowledge of the species.
Illiger died young. His talents were such as to raise among his compatriots the highest hopes of his future eminence, and his death was a subject of just regret to all who knew what he had achieved so well at an early age, and who more gladly lent themselves to the anticipation of what he would afterwards have accomplished had his life been prolonged. Of his classification it has been written by a competent judge: "Neque apud veterem, neque apud recentiorum quendam auctorem ullum systema invenimus, quod tam sua perspicuitate, quam accurate, Illigeriano magis commendari mihi videatur." Many of his genera are indeed remarkable for their felicitous construction and consonance with the natural arrangement. They have in consequence been readily adopted by his more fortunate fellow-labourers in the same field, in whose works they will remain, and be handed down in ample attestation of the author's genius; but the system itself will suffer a partition, and ere long cease to be practically known under the form in which it was originally promulgated, and this mainly in consequence of his having adopted so many new names.
M. de Blainville is still alive, and the longer he lives the better for the sciences of anatomy and physiology, neither of which contains in its modern annals the name of a more accomplished or enlightened expounder of its mysteries than his own; but in the character of a naturalist, and in connection with the subject of nomenclature, he unfortunately sins more than all his predecessors. He really miscalls the objects of zoology most sadly, yet his knowledge of the essential bases of the science is no doubt too profound to admit of his applying it without new and important results. Hence the pity that these should not at all times be stated in such terms as not only to amalgamate more closely with the kindred labours of his contemporaries, but to fall rather more clearly within the comprehension of ordinary minds.
As it is not our intention in the present rapid sketch to enter into the distribution of the animal kingdom beyond the greater divisions called classes, we shall not exhibit the systems of the two first-named authors further than to say, that the former attended almost exclusively to entomology, the latter chiefly to the mammalia and birds. When we come to the divisions of our subject under their separate heads, tabular views or more detailed ana-
Animal Kingdom. lyses will be presented of the labours of these and other ingenious inquirers of the past and present times.
We have said that we regarded the system of Linnæus as the basis of all those by which it has been succeeded, and that without a knowledge of his classification it would be impossible to understand either the merits or defects of more recent systems. We shall therefore here present the classes into which the great Swedish naturalist divides the animal kingdom.
A heart with two auricles and two ventricles; blood warm and red.
CLASS I.—Viviparous animals, or such as suckle their young; commonly called quadrupeds, but including also the cetacea or whales. MAMMALIA.
CLASS II.—Oviparous animals, or birds.... AVES.
A heart with one auricle and one ventricle; blood cold and red.
CLASS III.—Animals breathing arbitrarily through lungs..... AMPHIBIA.
CLASS IV.—Fishes, or animals with gills... PISCES.
A heart with one ventricle, no auricle; blood cold and white.
CLASS V.—With antennæ; undergoing transformations. Insects..... INSECTA.
CLASS VI.—With tentacula, and undergoing no transformations. Worms, VERMES.
It may be observed, that the deservedly popular system of Linnæus, though it does not profess to be a natural method of classification, actually is so in many of its parts; nor can it be denied that, on the whole, it usually brings
Animal Kingdom. together as many groups of natural genera as occur in most systems that have been promulgated, especially if we take into consideration the period at which it was composed, and the comparatively scanty materials within his reach. Linnæus was probably aware of the extreme difficulty, we might say at once of the utter impossibility, of a perfectly natural arrangement; for he confesses, in his Philosophia Botanica, his inability to define the great divisions called orders, on account of their being so connected with each other by various points of affinity, as to form a map rather than a linear series; and the observation may be applied with equal truth to the subjects of the animal kingdom. In regard to the excellence of his genera themselves, their consonance with nature is rendered still more evident, by the great proportion of those which Cuvier and Latreille have retained as leading generic divisions in their recent works,—certainly the most skilful approaches which have yet been made in the establishment of a natural system. It has been asserted, and we believe with truth, that such naturalists as are perpetually intent on the abstract theory of classification, rarely attain the highest excellence in the discrimination or definition of the species,—the only distinctions possibly which have a real foundation in nature, and upon an accurate and extensive knowledge of which alone their theoretical systems can be substantially and permanently built. At all events, it is admitted that Linnæus is a guide almost infallible, in as far as concerns his wonderful facility in discovering the minor natural groups. If he could have combined these as well as he has defined them, his possession of the sceptre would have been still undoubted.1
M. Virey, in the first edition (1803) of the Nouveau Dictionnaire d'Histoire Naturelle, divides the animal kingdom into three great tribes, in accordance with the nature and distribution of the nervous system. As he appears to have been among the first to attribute a due degree of importance to that system in the classification of animals, we shall here exhibit a view of his general arrangement.
| Animals possessed of two nervous systems, the cerebro-spinal and the ganglionic..... | { | Heart with two ventricles and two auricles; blood warm, lungs cellular..... | { Man and Mammalia. |
| Heart with one ventricle and one auricle; blood cold..... | { Birds. | ||
| { Reptiles and Fishes. |
| Animals possessed of a single nervous system surrounding the œsophagus, with ganglia and branches; the sympathetic..... | { | A heart; branchiæ for respiration, mostly aquatic..... | { Mollusca. |
| { Cirrhipedes. | |||
| { Crustacea. | |||
| { | No heart; some vessels; trachææ for air or water..... | { Arachnides and Aptera. | |
| { Insects, winged, hexapod. | |||
| { Annelides and Helminthides. | |||
| { Intestinal worms. |
| Nervous system composed of molecules more or less perceptible; no distinction of sexes..... | { | Ascidia, inclosed in a tunic..... | Botrylli, &c. |
| Radiated animals; composed of rays parting from a centre..... | Echinodermata. | ||
| United in Polypiæ, or stony masses; coralligenous..... | Hydra and Polypus. | ||
| Microscopical..... | Corals and Ceratophytes. | ||
| Madrepores and Sponges. | |||
| Infusory Animals. |
The following summary will serve to illustrate M. Virey's views of the nature and characteristics of these three great divisions. We commence with the zoophytical tribe.
1st, Zoophytes are distinguished by an organic tissue of a very soft and pulpy nature, more or less diaphanous, and very contractile, though we cannot readily perceive
its muscular fibres. Its fundamental character consists in the extreme division of its nervous molecules throughout the flesh of these animals. Except in the Echinodermata and some other radiated classes, we can scarcely assert the existence of a nervous system amongst them (on which account they are named apathiques by Lamarck). Each portion of the body having its nervous molecule and its par-
1 Horæ Entomologica, part ii. p. 423.
Animal Kingdom. particular source of vitality, there is no common centre of sensation; thus division and generation are almost synonymous, and when individual parts are mutilated they are speedily reproduced. With these tribes the production of the species is in fact nothing more than a simple sprouting of a bud or offset, which separates itself from the maternal stalk. Zoophytical animals are of no sex, and thus resemble the agamous vegetables. The mouth is usually placed in the centre of the body, and is frequently surrounded by a species of unarticulated arms, radiating from a centre like the petals of many flowers. Several genera have only a single opening for the reception and rejection of the aliment. They have no viscera (excepting cæca in certain species); no heart, nor arterial nor venous vessels; no true circulation; no apparent organs of respiration. They are all aquatic, and water seems indeed the only fluid which pervades their economy. They may be called the cryptogamia of the animal kingdom. The sense of touch, and perhaps that of taste, seem the only ones enjoyed by these animals.
2dly, The Invertebrata present a greater complication of organs. Their principal character consists in a nervous system, extending itself, especially in the intestinal cavity, by numerous ramifications. In all the families of this great tribe, the nervous trunks surround the œsophagus, pass beneath the belly, and are furnished with many ganglions which supply branches to the different organs. That which is regarded as the brain in this tribe (named sensible by Lamarck) is nothing more than one or two ganglia situated above the œsophagus; but the particular distribution of the two nervous branches which spring from the collar of the gullet, and extend themselves over the body, gives rise to the divisions of molluscous and articulated animals established by Cuvier.
The last-named naturalist has observed, that in the mollusca the nervous system is composed of many ganglionic masses, dispersed throughout the organization, but connected by means of nervous filaments; and that the chief of these masses constitutes a kind of brain above the œsophagus. The mollusca have no skeleton; their muscles are attached to the skin, a soft contractile envelope, in which in many species are produced shells, or stony bodies of calcareous carbonate, formed by exudation or superimposed concretions. Besides the sense of touch, common to all animals, the mollusca are gifted with that of taste, and sometimes of sight; but the sense of hearing has not been remarked, except among the Cephalopoda or cuttle-fish. Their systems of digestion and secretion are rather complex; they are provided with a liver, and possess a circulating or vascular system, through which flows a humour or whitish sanies in place of blood. Their respiration is effected by aquatic or aerial branchiæ. The sexual organs are frequently united in the same individual.
Among the articulated classes (such as the crustacea, the arachnides, and insects) the nervous system consists of a double chord, extending from the head to the posterior extremity, and bearing knots or ganglia which correspond to the segments of the animal's body. The first ganglion above the œsophagus takes the place of what we call the brain in the higher animals, but it is not voluminous in proportion. All these animals are composed of segments or annular divisions, and their forms are elongated, and more or less cylindrical. Their skin or outer covering, always of a somewhat solid texture, becomes in many families hard, corneous, or even stony; and the muscles are attached to its interior. The greater number have arti-
culated members, feet, wings, pincers, palpi, &c. Many of these animals have closed vessels; and the crustacea have a heart and branchiæ. Others, according to Cuvier, are nourished by simple imbibition. Those insects which undergo metamorphoses are furnished with tracheæ or air-vessels for respiration, dispersed over their bodies. The organs of the sense of hearing are not discernible except among the crustacea; taste is universal, and also sight, except among the worms. Their jaws always ply laterally. The sexual organs are usually separate.
3dly, The Vertebrata comprehend all those animals which have a nervous system composed of ganglia, called sympathetic, for the functions of the internal life; and another symmetrical nervous system, of which the principal portions are inclosed in the cranium and spinal column, and which sends off chords for the functions of the external life. These are the most perfect and most highly endowed of all animals; they are named intelligens by Lamarck, and they are always endowed with five senses, of which never fewer than four are situated in the head. They possess a heart, red blood, a liver, lungs in the species which live in air, and branchiæ in those which live in water. An articulated, bony, symmetrical skeleton, placed in the interior of the body, gives support and solidity to the different parts. Such are man, mammiferous animals, and birds, which have warm blood, and respire by cellular lungs; such also are reptiles and fishes, of which the blood is cold. In all, the mouth has two horizontal jaws, and the members are never more than four in number.
The preceding are M. Virey's views of the distribution and general characteristics of the different classes of the animal kingdom.1 They contain a sound exposition of several of the substantial relations which exist between the different systems of the animal economy, and we present them to the reader even at the risk of afterwards repeating in part several essentialities of his doctrine, when we come to promulgate the views of his celebrated countryman and contemporary Baron Cuvier.
We shall next present a tabular view of the general distribution and primary divisions of animals according to the system of Lamarck. It will be observed that this author commences with the lowest tribes.
Animals without Vertebra.
* APATHETIC ANIMALS. (Apathiques.)
| 1. Infusoria. | } Characters. No brain nor elongated medullary mass; no special senses; forms various; rarely articulated. |
| 2. Polypi. | |
| 3. Radiata. | |
| 4. Vermes. |
(Epizoa.)
** SENSITIVE ANIMALS. (Sensibles.)
| 5. Insecta. | } Characters. No vertebral column; a brain, and generally an elongated medullary mass; some distinct or special senses; organs of movement attached beneath the skin; formed symmetrically of equal parts. |
| 6. Arachnides. | |
| 7. Crustacea. | |
| 8. Annelides. | |
| 9. Cirrhipedes. | |
| 10. Mollusca. |
Animals with Vertebra.
*** INTELLIGENT ANIMALS. (Intelligens.)
| 11. Pisces. | } Characters. A vertebral column, a brain and spinal marrow; distinct senses; organs of movement attached to parts of an interior skeleton; formed symmetrically of equal parts. |
| 12. Reptilia. | |
| 13. Aves. | |
| 14. Mammalia. |
Animal Kingdom. The author of the preceding arrangement has entered upon the discussion of certain preliminary points connected with the subject of classification, which may be regarded as composing the art rather than the science of Zoology. He inquires (in his introduction to the Hist. Nat. des Anim. sans Vert.) what are the operations to be performed for the execution of a good distribution of animals, and for the establishment of the necessary divisions of that distribution? These operations he states to be as follows: 1st, To assemble animals together according to a principle which is not arbitrary, and so as to form a general series, whether simple or ramified: 2dly, To divide this general series into different kinds of lesser divisions, of which the one shall be subordinate to the other; and with that view to make choice of and submit to certain suitable and convenient principles (principes de convenance): 3dly, To fix the rank of each sort of division after one general principle, previously established; as, for example,
- The rank of each primary group in the total series;
- That of the classical divisions of each primary group;
- That of the orders or families in each class;
- That of the genera in each family; and
- That of the species in each genus.
The execution of these three sorts of operations is regarded by Lamarck as indispensable; and that it is so has been long felt by naturalists, almost all of whom have more or less occupied themselves in the attempt, but always in an arbitrary manner—that is to say, without the previous establishment of principles deserving of general consent. The first of the operations alluded to—that which concerns the bringing together of species in such a manner as to form a general series—is an essential preparation, which ought to precede the other operations, and without which indeed the latter could not be executed. It tends, moreover, to enable us to discover the order of nature, with which it is so highly important that we should become acquainted. Although nature has necessarily followed a certain order in the formation of organized beings, and especially of animals, yet as she has now dispersed these animals, and commingled all the different races over the surface of the solid globe, or through the wide depth of liquid waters, the original order of formation is to a certain extent disguised, and so far imperceptible. We are therefore obliged, with a view to its ascertainment, to search after some means by which we may attain to that discovery, and to work out some solid principles to lessen the chance of error. In regard to this, the most important step has been already attained, when we acknowledge the interest inspired by affinities or relations, and the necessity of understanding these, with a view to submit to them, as to a test, the various parts of our general distribution. It may thus be perceived, that in order to establish a good distribution of animals, in such a manner that its solidity shall run no risk of being enfeebled by the arbitrary nature of opinion, it is necessary first of all to assemble our species according to well-determined affinities; after which we may, without inconvenience, trace out the lines of demarcation which separate the groups called classes, and those other subordinate groups of which the establishment is so advantageous, provided the natural relations are in nowise compromised by their formation. It may perhaps be proper shortly to inquire into the nature of these relations, their different degrees, and the exact uses which it becomes us to make of such as we ascertain and acknowledge. We shall then be enabled with greater facility to determine the principles which it is fit to establish.
Relations, according to Lamarck, are those traits of resemblance or analogy which nature has bestowed, as
well on her different productions when compared among themselves, as on the different parts of those same productions when compared with each other. These traits of resemblance and affinity are so necessary to be known and understood, that no methodical distribution can be established on a sure foundation, if the objects which it embraces are not arranged according to the law which they prescribe. Relations are of different orders, some being very general, others less so, and many altogether special or particular. Moreover, although, in general, relations belong to nature, all are not the direct result of her operations in regard to her productions; for among the relations which we perceive between the compared parts of different beings, there are many which result merely from a modifying cause. Thus the relations of exterior form, which are so apparent between the cetacea and fishes, can only be attributed to a property resulting from the dense medium which each inhabits, and not to any direct plan in the operations of nature in regard to both. It is necessary then carefully to distinguish those obvious and acknowledged relations which pertain to the direct operations of nature in the progressive organization of animal life, from certain others, equally obvious and acknowledged, which result from the influence of local circumstances, or from the peculiar habits which different races have in some instances been forced to acquire.
Relations of the last-named nature, though certainly of greatly inferior value to the former, are by no means limited in their influence and exhibition to external characters alone; for it may be demonstrated that the external cause which possesses the power to modify the direct operations of nature frequently exercises an obvious influence on several internal organs. It becomes the more necessary then to establish certain rules, devoid of arbitrary qualities, to enable us justly to appreciate the nature and value of these relations; and it may be established as a principle in zoology, that it is from the interior organization that the most essential are to be obtained. This principle is well founded if it expresses the pre-eminence which ought to be accorded to general considerations, gathered from the interior organization, over those derived from external parts. But if, instead of using it in this manner, we apply it to particular cases of our own choosing, and without pre-established rule, it is capable of great abuse; and we shall arbitrarily assign to relations presented by such or such system of internal organs, a preference over certain others, although the relations of the latter may in reality be of greater importance. By this means, sufficiently convenient for the changeable views of individual authors, we admit into various parts of our distribution inversions in every way contrary to the order of nature.
It is true, as has been already observed, that a cause which modifies organization not only acts on the exterior parts of animals, but also produces various modifications in their internal structure. It follows, that it is incorrect to suppose that the relations which exist between the races, and especially between the genera, the families, the orders, or even in certain cases the classes of animals, can always be decided merely from the isolated consideration of any internal organ, arbitrarily selected. On the contrary, Lamarck is of opinion that the relations of which we speak cannot be suitably determined except by a consideration and comparison of the whole of the interior organization, and, auxiliarily, by that of certain special internal organs which assured principles have demonstrated to be the most preferable and important.
The second question proposed by M. Lamarck is the following: What are the principles by which we ought to be guided in our operations, so as to exclude from these
Animal Kingdom. whatever is arbitrary? Our author is of opinion that it is by the precise discrimination of each sort of relationship, and by aid of a determination, substantial and explained, of the preference which ought to be accorded to one kind over another, that we shall discover principles proper to regulate all the parts of our general distribution of animals. It is necessary then to determine the principal kinds of relations which ought to be employed to attain this end, and then to fix the superiority in value which one kind possesses over another. The following is the classification of Lamarck in further illustration of this subject.
* Relations between Comparative Organizations, deduced from the whole of their parts.
These relations, though general, manifest themselves in different degrees, according as we seek for them among races compared in themselves, or among groups of animals of different races compared with each other. It is necessary then to distinguish several kinds.
First kind of general relations.—These seem immediately to connect races or species with each other. They are of necessity the first, because it is they which furnish the greatest of the relations between animals which differ from each other. The zoologist who determines it, taking into consideration all the parts of organization, as well interior as exterior, admits not of this sort of relation, unless when it presents the smallest and least important difference. We know that animals which resemble each other perfectly, both in their internal and external organization, can be nothing more than individuals of the same species. In this case the relation is not considered, as such animals offer no distinction. But those which present among themselves a difference, tangible, constant, and at the same time the smallest possible, are connected by the greatest and most immediate of relations, if they present elsewhere a great resemblance in all the parts of their interior organization, as well as in the greater proportion of their external features. And this sort of relation does not demand a consideration of the degree of composition or relative perfection of the animal organization, for it determines itself in all the ranks of the scale. It is so easy to seize, that every one acknowledges it at first sight; and it is by employing it that naturalists have formed those smaller portions of the general series called genera, notwithstanding the arbitrary nature of their limits. Thus, in this first kind of relation, which may be called the relation of species, the difference between the objects compared is the smallest possible, and need only be sought for in the particularities of form or of the external parts of individuals.
Second kind of general relations.—This embraces the agreements which exist between groups of different animals when compared together. It may be named the relation of groups; and, to acquire a knowledge of its nature, we must no longer occupy ourselves essentially with the particulars of the general form, nor with those of the external parts, but almost solely with the interior organization, considered in all its parts. It is this kind chiefly which ought to furnish the differences by which we distinguish the groups from each other; and it is inferior in one or more degrees to the first kind in the quantity of resemblances which exist between the compared objects. It serves to form the families, by connecting the genera with each other; to institute the orders, or the sections of the orders, by uniting several families; and, lastly, it determines the classical groups into which we ought to partition the general series. The relations of which we now speak cannot, however, be employed to determine the rank of the great masses of that series, but only to form
diverse combinations for establishing and distinguishing these masses.
From the consideration of these relations, the two following principles may be deduced.
First principle.—The general relations of the second kind do not require a perfect resemblance in the interior organization of the compared animals. " Ils exigent seulement que les masses rapprochées se ressemblent plus entr'elles, sous ce point de vue, qu'elles ne le pourraient avec aucune autre." (Anim. sans Vert. tome i. p. 355.)
Second principle.—The greater and more general the compared masses, the more will such masses differ in their internal structure. Thus the families present a less difference in the interior organization of the animals by which they are constituted, than the orders or classes.
Third kind of general relations.—We may denominate relations of rank those which serve to determine the position in the great series, and which, proceeding from a fixed point of comparison, effectively show among the compared objects a relation, whether great or small, in the composition or perfection of the organization. This kind is obtained by comparing any organization whatever, taken in the totality of its parts, with any other given organization which may be presented as a point of departure or of comparison. It is then determined, by the resemblance, greater or less, which is found between the two compared structures, to what extent that which we compare departs from or approaches to that which is given as a point of comparison. We shall see that this sort of relation is the only one which ought to serve for regulating the rank of all those important primary masses into which we divide the animal kingdom.
If we consider the question concerning the choice of a particular organization, from or towards which to remove or approximate other organizations successively, according to their greater or less resemblance, it becomes evident that the selection ought to fall on one or other extremity of the animal kingdom (as in that case there would be no uncertain balancing), and the best known extremity should have the preference. Thus, in setting out from the most perfect and highly finished structure, we should, in the determination of all the ranks, proceed from the most composite to the most simple, and should close the series by the most imperfect and least organized of the whole.
Of all forms of structure, that of man, considered in its totality, is at once the most composite and complete. From this M. Lamarck concludes that the more any animal organization approaches that of the human race, the more it advances towards comparative perfection and its own completion. This being the case, the organization of man is with that author the point of comparison and departure from which to judge of the relation, whether near or distant, of every form of animal structure, and by which we are to determine the rank which those forms, or the groups which they constitute, ought to occupy in the general series. The organization alluded to, considered in the totality of its parts, furnishes the means by which to judge of the degree of composition and perfection of other animal structures also regarded in their totality. And in doubtful cases it is not difficult to rid ourselves of uncertainty and embarrassment, by having recourse to the fourth kind of relations, or to those principles which concern the comparison of the different organs separately considered, and establish a predominating value and influence among certain of those organs when compared with others. Thus, our point of departure or comparison being found, the rank of all the divisions may be assigned with facility by the aid of the principles which follow.
Animal Kingdom. First principle.—For the determination of the rank of each mass in the series,—the most complicated and complete of animal organizations being selected as the point of comparison,—the more another form of animal structure, considered in the whole of its parts, resembles that of the fore-chosen, the more it will approximate towards it by its relations; and reciprocally in the converse cases.
Second principle.—Among the organizations of which the plans are different from that which comprehends the particular structure selected as the point of comparison, those which offer one or more systems of organs similar or analogous to such as form a portion of that with which they are compared, shall rank superior to those possessed of a smaller number of these organs, and, a fortiori, to those in which they are wanting.
With the assistance of the three kinds of relations above indicated, and the principles deducible from them, M. Lamarck regards it as easy to determine the distinctions of species, and those of the various larger groups which species form; and to decide, in a manner by no means arbitrary, the rank and station of each group in the great series. If this be true, the science will cease to be as vacillating in its onward march as it has hitherto proved.
But our efforts would be incomplete, and would still leave too large a field for the exercise of arbitrary opinions, if no attempt were made to establish and define the value of particular relations,—that is to say, of those which are obtained by the comparison of particular internal organs, considered in an isolated manner in different animals.
** Relations between similar or analogous parts taken separately in the organization of different animals, and compared with each other.
The fourth kind of general relations merely embraces particular relations between unmodified parts. It is drawn from the comparison of parts separately considered, and which, in the system of organization to which they belong, offer no real anomaly. The consideration of this kind is sometimes of great consequence in assisting to decide in doubtful cases, when we are anxious to determine, among certain compared groups, to which the superiority of rank ought to be assigned. Such cases sometimes occur where the whole of the parts of the interior organization present no means of deciding, in an unarbitrary manner, to which of two organizations the superiority belongs. It is especially in the formation and position of the orders, sections, families, and even genera, of each class, and consequently in the assignment of the rank of all these inferior groups, that the employment of this fourth kind of relations is of advantage; because, in regard to such groups, the principle of the third sort of relations is frequently very difficult of application; and thus arbitrary modes of arrangement are introduced, most baneful to the science, by exposing the works of naturalists to a continual variation in the determination of the relations which ought to fix the composition of the groups, and their order of position. In fact, as many animals, really connected by the general characters of their class, present remarkable differences in certain of their interior organs, and yet at the same time exhibit equally striking resemblances in others, we feel that, in order to appreciate the degree of importance possessed by the relations which exist between particular organs, we must have recourse to certain regulating principles in our determinations, to avoid arbitrary conclusions. The two following principles are proposed by Lamarck, to enable us to appreciate the relations observable between particular internal organs in different animals compared with each other.
First principle.—Between two internal organs, or systems of internal organs, separately considered and com-
pared, that of which nature has made the most general employment ought to have the pre-eminence assigned it in the value of the relations which it presents. According to this principle, the following is the order of importance which we ought to attribute to the particular organs which nature has employed in the interior organization of animals:—
| The organs of digestion; | The organs of production; |
| The organs of respiration; | The organs of sensation; |
| The organs of movement; | The organs of circulation. |
Thus, when we take into view the greatest generality of employment of the particular organs of which nature makes use in the interior organization of animals, we perceive that the organs of digestion occupy the foremost rank,—those of circulation the last. We have thus an order of value or precedence, in regard to these important organs, capable of regulating, in doubtful cases, the preference which one relation merits over another.
Second principle.—Between two different modes of the same organ, or system of organs, that which is most analogous to the mode employed in a superior or more composite and complete organization, merits the preference in the relations which it exhibits. If, for example, we desire to employ a relation afforded by the organs of respiration,—to judge of the preference which it deserves over that offered by other organs,—we are obliged, according to the principle above established, to keep in view the following consideration:—Although the system of organs provided for respiration is very widely employed in the organization of animals, since, with the exception of the polyped and infusorial classes, all the rest possess a respiratory system, yet the mode of that system not being the same in all the classes by which it is exercised, we assign a higher value to the true lung than to the branchia, to the latter than to the aeriferous tracheæ, and to these than to the aquiferous tracheæ. According to this view, we may judge whether the mode of respiratory organs of which we wish to employ the relation, is sufficiently high in value to permit our yielding to it a preference over a relation deduced from some other kind of organs.
The fifth kind of relations embraces the particular relations observable between the modified parts. It requires that, among the parts compared, we should discriminate between that which is due to the real plan of nature, and that which pertains to the modifications which that plan has experienced from accidental causes. Thus this class of relations is derived from parts which, considered separately in different animals, are not in the state in which they ought to be, according to the plan of organization to which they belong. To judge of the degree of importance which ought to be accorded to a relation, and the preference which it deserves over another, it is a matter of no slight consequence to distinguish if the form, the increased or diminished development, or even the entire disappearance of the particular organs under consideration, belongs to the plan of organization of the animals subjected to such modifications; or whether the state of these organs is not rather produced by a modifying and determinable cause, which has altered or annihilated that which nature had executed, and would have maintained, but for the influence of that later cause. "For example," says Lamarck, "it would have been impossible for nature to furnish a head to the infusoria, the polypi, or the radiata, &c.; for the condition of these bodies, and the degree of their organization, did not permit it; and it was only on arriving at the class of insects that a genuine head could be supplied." Now, as nature never retrogrades in her operations, we naturally expect, that when once arrived at the formation of insects, and consequently of heads, the recipients of the special senses, all animal organizations
Animal Kingdom. superior in composition to that of insects will also exhibit these organs. This, however, is not universally the case; because no distinct head is observable among the annelides, the cirrhipeles, and many mollusca, all of which are generally regarded as superior to the class of insects. "Une cause étrangère à la nature, en un mot, une cause modifiante et déterminante, s'est donc opposée à ce que les animaux cités soient pourvus d'une véritable tête." (Anim. sans Vert. tome i. p. 363.) And that cause appears to have operated sometimes by hindering to a greater or less extent the development of that part of the body, and at other times by effecting its complete destruction. We find the same thing in regard to eyes and teeth, and to various other parts both of the internal and external structure; because a modifying cause has had the power to alter, enlarge, diminish, or even to effect the total disappearance of these organs. We may perceive, then, that the relations obtained from the consideration of changed or modified parts must be of very inferior value to those furnished by the same parts existing in a state conformable to the plan of nature. Hence results the following
Principle.—Whatever nature has directly formed deserves a pre-eminence in value over that produced by a fortuitous cause, which has modified the work of nature; and in the choice of a relation to be employed, we should assign the preference to every organ, or system of organs, which we find existing as it ought to do according to the plan of organization of which it forms a part, over that organ, or that system of organs, of which either the condition or existence has resulted from a modifying cause, extraneous to original nature.
When two different organs, between which a choice is to be made, are both found to be changed or altered by a modifying cause, the preference should be given to that which is least removed by such a modification from the condition in which it would have existed according to the plan of organization of which it formed a part.
The third question proposed by M. Lamarck is as follows:—What disposition or mode of arrangement should be given to the general distribution of animals, so as to render it conformable to the order followed by nature in the production of these beings? To resolve this question, we must also endeavour to deduce some principle from nature herself, with a view to such conformity; for if we were to determine the general distribution of animals according to the progression which exists in the animal organization, it appears that we might, in that progression, proceed with as much reason from the most composite to the most simple, as from the most simple to the most composite. Such a proceeding, however, could not rest on a proper basis: for we shall find that nature, consulted in the order of her operations in regard to animals, indicates the following principle, which excludes all arbitrary selection:—Nature always operating in a gradual manner, and consequently never producing animals otherwise than successively, has obviously proceeded in such a production from the most simple towards the most complex. We ought, therefore, in our general distribution, to imitate the order which nature herself has followed. "J'ai, en effet,
montré," says Lamarck, "dans ma Philosophie Zoologique (tome i. p. 269), que, pour rendre la distribution générale des animaux conforme à l'ordre qu'a suivi la nature en produisant toutes les races qui existent, il fallait procéder du plus simple vers le plus composé,—c'est-à-dire, qu'il était nécessaire de commencer cette distribution par les plus imparfaits des animaux, et les plus simples en organisation, afin de la terminer par les plus parfaits, par ceux qui ont l'organisation la plus composée." He further observes, in his Anim. sans Vert. "Cet ordre est le seul qui soit naturel, instructif pour nous, favorable à nos études de la nature; et qui puisse, en outre, nous faire connaître la marche de cette dernière, ses moyens, et les lois qui régissent ses opérations à leur égard." Although we may find it less pleasant or conformable to our habitual taste to present at the head of the animal kingdom creatures of the most limited perceptions, excessively minute in size, and of scarcely any consistence in their parts,—yet as in all things it is necessary to consider the end in view, and the means which conduct towards it, Lamarck is of opinion that the arrangement established by usage in the distribution of animals is precisely that which leads us away from the point in view, as well as the least favourable for our instruction, and that it opposes the greatest number of obstacles in the way of our perceiving the plan, the order, and the means employed by nature in her operations concerning the animal world.
If in the study and examination of living bodies we had no other object in view than to distinguish the one from the other by characters deduced from their external forms—and if we were not desirous to regard their various and wonderful faculties otherwise than as simple matters of amusement, not altogether unfitted to excite the curiosity of a leisure hour—then the most ordinary and artificial system would suffice; for in that case it would be useless to occupy ourselves with researches concerning the affinities of animals, or to study their internal structure. But all naturalists are now agreed regarding the high importance of these affinities, and the necessity of holding them ever in view in our general arrangement of the animal kingdom. The bat is no longer classed with birds merely because, like them, it wings its way through the air; nor are seals or whales regarded as fishes because the dense nature of the medium which they inhabit requires a somewhat analogous form; neither are cuttlefish and polypi confounded together, though the mouth of each is surrounded by numerous arms.
We have dwelt at greater length than we intended on the system of Lamarck, or rather on the views by which he seeks to illustrate the principles on which his system professes to be built. Though occasionally prolix, and sometimes rather obscure, his observations, on the whole, are well deserving of an attentive consideration. Like most of his countrymen, he is unfortunately more regardful of secondary causes, and more anxious to illustrate their fitness and sufficiency, than he is ready to acknowledge the source from which they spring, or to admire the wisdom and beneficence of their providential institution.1
1 "The doctrine of Epicurus, that the Deity concerns not himself with the affairs of the world or its inhabitants, which, as Cicero has judiciously observed (De Nat. Deor. lib. i. ad caeleum), while it acknowledges a God in words, denies him in reality, has furnished the original stock upon which most of these bitter fruits of modern infidelity are grafted. Nature, in the eyes of a large proportion of the enemies of revelation, occupies the place, and does the work, of its great Author. Thus Hume, when he writes against miracles, appears to think that the Deity has delegated some or all of his powers to nature, and will not interfere with that trust (Essay, ii. 75); and, to name no more, Lamarck, treading in some measure in the steps of Robinet (who supposes that all the links of the animal kingdom, in which nature gradually ascends from low to high, were experiments in her progress towards her great and ultimate aim, the formation of man—Barclay on Organization, &c. 263), thus states his opinion:—"La nature, dans toutes ses opérations, ne pouvant procéder que graduellement, n'a pu produire tous les animaux à la fois; elle d'abord n'a formé que les plus simples; et passant de ceux-ci jusques aux plus composés, elle a établi successivement en eux différents systèmes d'organes particuliers, les a
Animal Kingdom. We shall now proceed to the system of another naturalist, also highly accomplished in the science, M. Dumeril, the friend and pupil of Baron Cuvier, and to whose collection of the oral demonstrations of his great master we were originally indebted for the publication of the Leçons d'Anatomie Comparée.
Table of the Classification of Animals, according to the System of Dumeril.
| Internally articulated; vertebrated; | { | with mammæ; viviparous..... | 1. MAMMIFERÆ. |
| without mammæ; oviparous; | lungs; feathers, wings..... | 2. BIRDS. | |
| no lungs; neither feathers nor wings..... | 3. REPTILES. | ||
| Externally articulated; invertebrated; | { | branchiæ..... | 4. FISHES. |
| articulated members; tracheæ..... | 5. INSECTS. | ||
| no articulated members; branchiæ..... | 6. CRUSTACEA. | ||
| Not articulated; | { | distinct respiratory organs; vessels..... | 7. WORMS. |
| no respiratory organs; no vessels..... | 8. MOLLUSCA. | ||
| 9. ZOOPHYTES. |
The ensuing tabular view exhibits the classification proposed by M. de Blainville. We shall leave the reader to judge for himself of the propriety of introducing so many new appellations for groups constructed long ago.
His nomenclature is no doubt intimately connected with his views of the structure and physiology of animals, and is highly approved of and adopted by many competent judges of the science.
SYNOPTICAL TABLE of the PRIMARY, SECONDARY, TERTIARY, and QUATERNARY DIVISIONS of the ANIMAL KINGDOM, denominated Sub-Kingdoms, Types, Sub-Types, and Classes, by M. de Blainville. From the Principes d'Anatomie Comparée of that author.
| ANIMAL KINGDOM. | ||||
|---|---|---|---|---|
| I. Sub-Kingdom. Regular or ARTIOMORPHOUS Animals. ARTIOZOAIRES. |
articulated..... | Type I. interiorly. OSTEOZOAIRES. |
I. Sub-Type. Provided with mammæ and ...hairs..... VIVIPAROUS. |
1. PILIFERES or MAMMALIA. |
| II. Sub-Type. Without mammæ. |
||||
| Type II. exteriorly. ENTOMOZOAIRES, or articulated animals. With appendages. |
OVIPAROUS. | feathers..... scales..... naked skin..... fins..... |
2. PENNIFERES or BIRDS. 3. SQUAMMIFERES or REPTILES. 4. NUDIPELLIFERES—AMPHIBIA. 5. PINNIFERES or FISHES. |
|
| Provided with | 3 pair..... 4 pair..... 5 pair..... variable..... 7 pair..... = the segments |
6. HEXAPODES. 7. OCTOPODES. 8. DECAPODES. 9. HETEROPODES. 10. TETRADECAPODES. 11. MYRIAPODES. 12. CHITOPODES. |
||
| articulated to the number of | 13. APODES. | |||
| not articulated..... | ||||
| sub-articulated..... | Type III. MALENTOZOAIRES or MOLLUSCARTICULES..... |
14. NEMATOPODES. 15. POLYPLAXIPHORES. |
||
| not articulated..... | Type IV. MALACOZOAIRES..... Molluscous animals. |
The head..... | distinct..... not distinct... |
16. CEPHALOPHORES. 17. ACEPHALOPHORES. |
| sub-radiated..... | 18. ANNELIDAIRE. | |||
| II. Sub-Kingdom. Radiated or ACTINOMORPHOUS Animals. |
ACTINOZOAIRES. | normal or true..... | 19. CERATODERMAIRES. 20. ARACHNODERMAIRES. 21. ZOANTHAIRES. 22. POLYPIAIRES. 23. ZOOPHYTAIRES. |
|
| III. Sub-Kingdom. Irregular or HETEROMORPHOUS Animals. |
HETEROZOAIRES..... | 24. SPONGIAIRES. 25. MONADAIRES or MOLECULAIRE. 26. DENDROLITHAIRES. |
||
multipliées, en a augmenté de plus en plus l'énergie, et les cumulant dans les plus parfaits, elle a fait exister tous les animaux connus avec l'organisation et les facultés que nous leur observons." (Anim. sans Vertèbr. i. 123.) Thus denying to the Creator the glory of forming those works of creation, the animal and vegetable kingdom (for he assigns to both the same origin, ibid. 83), in which his glorious attributes are most conspicuously manifested; and ascribing them to nature, or a certain order of things, as he defines it (214)—a blind power, that operates necessarily (311), which he admits, however, to be the product of the will of the Supreme Being (216). It is remarkable, that in his earlier works, in which he broaches a similar opinion, we find no mention of a Supreme Being. (See his Système des Animaux sans Vertèbres, Discours d'Ouverture.) Thus we may say, that, like his forerunner Epicurus, He told, dum oratione relinquit Deum. But though he ascribes all to nature, yet, as the immediate cause of all the animal forms, he refers to the local circumstances, wants, and habits of individual animals themselves: these he regards as the modifiers of their organization and structure (162).
Animal Kingdom. Let us here note, that M. Desmoulin, in the 2d edition of Dr Magendie's Physiology (1825), has exhibited a system in which the principles of Cuvier and De Blainville are joined in one.
A learned and ingenious Scotsman, Mr William Sharpe Macleay, is the author of several profound and original views in natural history. The unbroken and continuous succession, or linear series, in which systematic writers had previously regarded the objects of their contemplation, was first deviated from by Lamarck, who, in his supplement to the first volume of his Animalles sans Vertèbres, presented the Invertebrata in a double subramose series, consisting of articulated and inarticulated animals. The following are the principal bases of Mr Macleay's system.1
1. That all natural groups, whether kingdoms or any subdivision of them, return into themselves; a distribution which Mr Macleay expresses by circles.
2. That each of these circles is formed precisely of five groups, each of which is resolvable into five other smaller groups, and so on till we reach the extreme term of such division.
3. That proximate circles or larger groups are connected by the intervention of lesser groups, denominated osculant.
4. That there are relations of analogy between the corresponding points of contiguous circles.
The author has represented his system by tables of circles, inscribed with the names of the five primary divisions of each group. The following table exhibits his general view of the animal and vegetable kingdoms:
It will be perceived by the preceding diagram, that Mr Macleay divides the animal kingdom into five great subkingdoms, viz.
1. ACRITA, composed of the infusoria, the polypi, the corallines, the tœnæ, and the least organized of the intestinal worms.
2. RADIATA, containing medusæ, star-fish, sea-urchins or echini, and others.
3. ANNELOSA, consisting of insecta, arachnida, and crustacea.
4. VERTEBRATA, constituted by beasts, birds, reptiles, amphibia, and fishes.
5. MOLLUSCA, including the numerous tribes of shell-fish or marine testacea, fresh-water shells, snails, slugs, &c. which, from the analogies presented by their soft or mucous substance, the peculiarities of their nervous system, and the general imperfection of their senses, appear as it were to return again to the acrita, though allied to the vertebrata by characters drawn from the possession of a heart and a circulating system.
The ensuing set of circles exhibits the further subdivision of the five sub-kingsdoms into classes.
The osculant classes are such as are placed between the circles. In the molluscous circle two classes are still wanting to complete the quinary arrangement of that great division. According to Mr Kirby, the number five, assumed by Mr Macleay as a principal basis of his system, and as consecrated in nature, ought to yield to the number seven, which is consecrated both in nature and scripture. Metaphysicians enumerate seven principal operations of the mind, musicians seven principal tones, and opticians seven primary colours. In scripture, the abstract idea of this number is, completion, fullness, perfection. Mr Kirby seems to think that Mr Macleay's quinaries may be found resolvable into septenaries, in consequence of future investigations.2
We shall enter at greater length into a detailed expo-
To show the absurd nonplus to which this his favourite theory has reduced him, it will only be necessary to mention the individual instances which, in different works, he adduces to exemplify it. In his Systeme he supposes that the webfooted birds (Anseres) acquired their watery feet by frequently separating their toes as far as possible from each other in their efforts to swim. Thus the skin that unites these toes at their base contracted a habit of stretching itself; and thus in time the web-foot of the duck and the goose was produced. The waders (Grallæ), which, in order to procure their food, must stand in the water, but do not love to swim, from their constant efforts to keep their bodies from submersion, were in the habit of always stretching their legs with this view, till they grew long enough to spare them the trouble!!! (13). How the poor birds escaped drowning before they had got their web-feet and long legs the author does not inform us. In another work, which I have not now by me, I recollect he attributes the long neck of the camelopard to its efforts to reach the boughs of the mimosa, which, after the lapse of a few thousand years, it at length accomplished!!! In his last work he selects as an example one of the Mollusca, which, as it moved along, felt an inclination to explore by means of touch the bodies in its path: for this purpose it caused the nervous and other fluids to move in masses successively to certain points of its head, and thus in process of time it acquired its horns or tentacula!! (Anim. sans Vertèbr. i. 188.) It is grievous that this eminent zoologist, who in other respects stands at the head of his science, should patronize notions so confessedly absurd and childish." (Introduction to Entomology, by Kirby and Spence, vol. iii. p. 349.)
1 See Horn Entomology, and Kirby & Spence's Introduction to Entomology, vol. iii. p. 12.
2 Introduction to Entomology, vol. iii. p. 15. The quinary system, in its application to insects and other annulose animals, is pretty fully developed by its ingenious author in his Horn Entomology, already more than once referred to. An excellent paper by Mr Vigors, on the classification of birds, in accordance with the same system, will be found in the 14th volume of the Transactions of the Linnean Society.
Animal Kingdom. sition of the quinary system of arrangement under the articles Entomology and Ornithology.
Cuvier divides the animal kingdom into four principal branches. Setting aside all accessory and artificial characters, he proceeds upon the consideration of the essential structure of animals, and thus deduces four great groups or separate types of form, to one or other of which all the minor divisions may be ultimately referred.
In the first of these forms the brain, and the great central trunk of the nervous system called the spinal marrow, are protected by strong bony coverings—the cranium and vertebral column. To the sides of that column are attached the ribs and the bones of the anterior and posterior members. All the classes of this primary division are provided with red blood, a muscular heart, a mouth with two horizontal jaws, and special organs of vision, hearing, taste, and smell, placed in the head or upper and anterior portion. They have never more than four members; their sexes are always separate; and they nearly resemble each other in the distribution of their medullary masses, and the principal branches of their nervous system. On examining more narrowly the constituent parts of the classes which compose this great assemblage, it is easy to discover many striking analogies both of form and structure, even in those groups which are most distantly related to each other; and from the human species to the last of the fishes there exists an obvious conformity to the same general plan. The name of VERTEBRATED ANIMALS is bestowed on this division, on account of their being possessed of a vertebral column or back-bone. The following are the principal groups or classes into which it is further divisible.
FIRST PRIMARY DIVISION: ANIMALIA VERTEBRATA.
- Class 1st. Man, mammiferous land-animals, and cetacea.
- Class 2d. Birds.
- Class 3d. Reptiles.
- Class 4th. Fishes.
The second great division possesses no skeleton. The muscles are attached to the skin, which forms a soft contractile envelope; and many of the species are protected by hard coverings, commonly called shells, which are supposed to occupy in the cutaneous system of this form of animal life the same station as the mucous membrane of the preceding division. The nervous system is contained along with the viscera within this general envelope, and is composed of many dispersed portions, of which the principal, placed above the œsophagus, may be regarded as representing the brain. Of the four special senses it is impossible to discover the organs of more than two, taste and sight; and even of these the last is frequently wanting. The organs of hearing are visible only in one family. The system of circulation is however complete; there are particular organs for the performance of respiration; and the functions of digestion and secretion are almost as complicated as in the vertebrated classes. The subdivisions of this second form are called MOLLUSCOUS ANIMALS; and although the external configuration of their parts does not exhibit the same agreement as that of the vertebrated classes, there is always a corresponding resemblance in their essential structure and functions. The following are the classes of this branch of the animal kingdom.
SECOND PRIMARY DIVISION: ANIMALIA MOLLUSCA.
- Class 1st. Cephalopoda, e.g. cuttle-fish, nautili, belemnites, argonauts, &c.
- Class 2d. Pteropoda. Genus Clio, &c.
- Class 3d. Gasteropoda. Slugs, snails, and numerous groups of turbinated shells.
- Class 4th. Acephala. Oysters, mussels, and other bivalve shells, &c.
- Class 5th. Brachiopoda. Terebratulæ, &c.
- Class 6th. Cirrhopodes. Barnacle shells, &c. Lepas and Triton. (Linnaeus.)
The third great preponderating form is represented by insects and other analogous classes. Their nervous system consists of two long ventral or sublateral chords, which swell out at intervals into knots or ganglia. The first of these ganglia, placed above the œsophagus, is analogous to the brain, although it does not exceed in size and scarcely in importance the ganglia of the lengthened cords, with which it communicates by means of a ring which embraces the œsophagus like a collar. The general covering of the body in this division is sometimes hard, sometimes soft, and is divided into segments by a certain number of transverse incisions. The muscles are always attached to the interior, and the body is usually, though not universally, provided with articulated members. It is among the classes of this form that we begin to perceive the passage from a system of circulation in closed vessels called arteries and veins, to nutrition derived from imbibition; and a corresponding passage from respiration in circumscribed organs to that performed by tracheæ or air-vessels, distributed over the whole body, is likewise observable. The organs of taste and sight are the most distinct in this branch; the organ of hearing is apparent only in a single family, although we can scarcely doubt that the sense exists in others in which the organ has not been ascertained. The following classes are ranked under this great form.
THIRD PRIMARY DIVISION: ANIMALIA ARTICULATA.
- Class 1st. Annelides. Serpulæ, nereids, leeches, earthworms, the hair-eel, &c.
- Class 2d. Crustacea. Crabs, lobsters, shrimps, &c.
- Class 3d. Arachnides. Spiders, scorpions, mites, &c.
- Class 4th. Insecta. Beetles, flies, butterflies, &c.
In the three preceding divisions, the organs of movement and of sensation are disposed symmetrically on both sides of an axis, with an anterior and posterior portion differing from each other. Among the zoophytes, which form the last great division, the organs are usually disposed in a radiated form. They approach the nature of plants in the extreme simplicity of their structure. They have no distinct nervous system, nor organs of the special senses; and it is barely possible to detect in a few of the species some slight vestige of the circulating system. Their respiratory organs are almost always on the surface of their bodies. The greater proportion of the classes exhibit no other intestine than a sack or cœcum, and the composition of the last groups of all presents only a homogeneous pulpy mass, sensible, and endowed with motion. From a consideration of their most usual forms, the classes of this order are named RADIATED ANIMALS. They are as follows:—
FOURTH PRIMARY DIVISION: ANIMALIA RADIATA.
- Class 1st. Echinodermata. Star-fish, sea-urchins, &c.
- Class 2d. Entozoa. Intestinal worms.
- Class 3d. Acalephæ. Sea-nettles, actinæ, medusæ, &c.
- Class 4th. Polypi. Corals, madrepores, sponges, &c.
- Class 5th. Infusoria. Infusory and other microscopic animals.
Animal Kingdom
||
Animalcule.
Such are the great outlines of a system which, considered in its generality, is certainly the most satisfactory which has yet appeared. Particular departments may have been filled up, modified, and perhaps improved by ingenious observers, sedulous within a limited sphere (and of these ameliorations we shall be careful to avail ourselves when we come to enter upon a detailed view of each of the classes of the animal kingdom); but the construction and position of the principal groups, their real as well as relative characters, are developed in the system of the great French anatomist, in a manner more clear and accordant with nature than in any other yet promulgated. We shall therefore in the course of this work adhere, with some slight transpositions, the reasons for which will be stated in their proper place, to the classes of Baron Cuvier. The greater extent and importance of some of these, in comparison with others, will induce us to bestow more attention and a larger space to their illustration; and as certain of the primary divisions, such as the Mollusca and Radiata, contain a greater number of classes, if not of less importance, at least by no means so strongly characterized or contradistinguished from each other as are those of the vertebrated tribes, we shall, in presenting the history and nomenclature of such classes, group them together in such a manner as to exhibit them to the reader either under one of the great primary divisions, or as an intermediate subdivision, containing one or more classes. For example, the article MOLLUSCA of this work will present consecutively under a single head the history and classification of the six classes contained in the second primary division so named;—but the four classes of vertebrated animals will be each discussed in a separate treatise. Thus mammiferous animals, birds, reptiles, and fishes, will form the articles MAMMALIA, ORNITHOLOGY, REPTILIA, and ICHTHYOLOGY. The Classes of the third primary division, viz. Annelides, Crustacea, Arachnides, and Insecta, will (with the exception of the first, referred to Helminthology) likewise be treated of under distinct
heads, in the alphabetical order, of the following terms:—CRUSTACEA, ARACHNIDES, and ENTOMOLOGY. In regard to the fourth primary division, that of the radiated animals, commonly called Zoophytes, the first class, named ECHINODERMATA, will be treated of separately under its own title; the second class, Entozoa, which contains the intestinal worms, will be grouped with the Annelides or red-blooded worms (as above excepted from the third primary division); and these two classes will be treated of together under the article HELMINTHOLOGY. The remaining classes of the Animalia Radiata, that is to say, the Acalephæ, the Polypi, and part of the Infusoria, as they form the last links of the animal kingdom, will come to be discussed with greater propriety at the concluding stage of this work, under the head of ZOOPHYTES. Finally, that portion of the infusorial class which we have excepted in the above distribution will be found described in the present volume under the word ANIMALCULE. This completes the exposition of our zoological system.
The following enumeration exhibits a view of the terms under which the principal subjects of zoology will be explained and illustrated in the course of this work.
| Systematic Arrangement. | Alphabetical Arrangement. |
|---|---|
| Mammalia. | Animalcules. |
| Ornithology. | Arachnides. |
| Reptilia. | Crustacea. |
| Ichthyology. | Echinodermata. |
| Mollusca. | Entomology. |
| Crustacea. | Helminthology. |
| Arachnides. | Ichthyology. |
| Entomology. | Mammalia. |
| Echinodermata. | Mollusca. |
| Helminthology. | Ornithology. |
| Zoophytes. | Reptilia. |
| Animalcules. | Zoophytes. (z. w.) |
ANIMAL Magnetism. See MAGNETISM, Animal.
ANIMALCULE.
ANIMALCULE, a diminutive term (from the word animal), applied by naturalists to those minute beings which become apparent in various fluids when subjected to the microscope. They were named infusoria (Infusoria) by Müller, one of the most celebrated observers in this department of zoology; and the appellation, however inapplicable, now occurs in the majority of scientific publications. Of course it applies with propriety only to such species as are developed through the medium of infused substances. Now we know, that of 400 species of Infusoria (commonly so called) described by Müller himself, not a sixth part were observed in any kind of infusions; whilst the remainder inhabited the most translucent waters, and speedily died when placed in impure or corrupted liquids. Even the word animalcule (or little animal) does not convey a positive or sufficiently restricted idea in relation to this particular class; because mites and certain polypi are extremely minute in their dimensions, and equally require the aid of microscopical investigation; and thus the term microscopics (microscopiques), recently proposed by M. Bory de St Vincent, is not less faulty than its predecessors. The size of an animal, in fact, bears no essential relation to the other conditions of its organization; and therefore we cannot infer its nature with any certainty
from a knowledge of its dimensions. At the same time it must be admitted, that the most simply organized, both of plants and animals, are also the most minute; and thus the Infusoria may be regarded as possessed of certain characters in common. We here adopt the word Animalcule, chiefly because it is the most familiar to the English reader.
The subjects of our present observations may be thus defined:—Animals invisible to the naked eye; more or less translucent; unprovided with members (the caudal, and other appendices, with which certain species are furnished, being scarcely regardable as such); no perceptible eyes; contractile in whole or in part; endowed with the sense of touch; deriving nourishment by absorption; generation (when not apparently spontaneous, and consequently incomprehensible) effected by division, or by the emission of gemmules or oviform bodies; inhabitants of liquids. They are the smallest and most simple of living creatures, but not less perfect than the other tribes; for though they possess the fewest faculties, their means are in every way adequate to their wants, and their vital energies proportioned to their sphere of enjoyment.
Among microscopical animals we find many species which, in their aspect and structure, present no analogy
1 The Pelozo globator, and a few others, which are just discernible without the aid of a microscope, form exceptions to the above character.
to other forms of animal life: they are merely moving molecules of the simplest organization, the exact nature of which it is sometimes difficult to determine, and which involve in deeper obscurity the mysterious line of demarcation by which we so often seek in vain to separate the animal from the vegetable kingdom. If, however, the true distinction between plants and animals consists chiefly in the irritability and power of contraction possessed by the latter, then the Infusoria, which are strongly endowed with these attributes, are indeed so far removed from the vegetable kingdom, that the name of Zoophytes, or animal plants, is inapplicable to the class to which they belong. In the extreme simplicity of their structure, they no doubt present some analogy to the least complicated tribes of plants, such as the algae and others; but it is a mere analogy, and not a connection of affinity,—for no alliance between these kingdoms has ever been demonstrated, although certain obscure phenomena may have presented difficulties in the way of our investigations. "We need not be surprised," Mr Macleay observes in his Horæ Entomologica, "that several of the Linnæan algae should be still hovering in a state of uncertainty between the two kingdoms; but, on the contrary, be prepared to expect additional proofs of the analogy which the two great divisions of organized matter bear to each other. The Agastria, or Agastriaire of De Blainville, are indeed animals, though they have neither distinct organs of sense, alimentary canal, nor even mouth,—though they have, in short, so far as our present knowledge of them would lead us to believe, no internal digestion whatever to execute, but trust for nourishment, like plants, to the absorption of their external pores. They must be esteemed animals on account of their peculiar irritability; but are vegetables in almost every other respect."
Our knowledge of the history of animalcules resulted from the improvement of the microscope by Hartzocker and Leeuwenhoek. The ancients were consequently unacquainted with the mysteries of this "invisible world;" and we are thus saved the tedium of a lengthened bibliographical investigation. Notwithstanding the observations of Hill, Baker, Ledermüller, Goeze, Gleicken, Roësel, Pallas, Needham, Spallanzani, and several other minute and laborious inquirers, it may be said that this branch of zoology only assumed a truly scientific form in consequence of the labours of a distinguished Danish naturalist, Otho Frederic Müller. His earlier works, such as the Vermium Terrestrium et Fluvialium Historia, and the Zoologica Danica Prodromus, presented very decided improvements in the knowledge and classification of animalcules. These emendations were transferred by Gmelin to the 13th edition of the Systema Naturæ of Linnæus, in which animalcules form the fifth order of the class of Vermes. But the work which had the rest been wanting, would alone have immortalized the name of Müller, appeared (posthumously) in 1786, under the title of Animalcula Infusoria, Fluvialia et Marina. It is illustrated by 50 plates, containing figures of 360 species variously represented. A later and very useful compendium of knowledge regarding microscopical animals forms a portion of the Encyclopédie Méthodique (46th livraison), in which Bruguière has reproduced the plates of Müller, with the addition of several others of equal accuracy from the third volume of Roësel's Insecten-belustigungen. The reader will there find descriptions of 28 plates, containing nearly 1100 figures representing 385 animalcular species.
Before proceeding further, we shall present a brief view of the system of Müller, as of high importance in itself, and the fundamental basis of the more recent and improved arrangements. It includes, however, several genera which are not now classed among the animalcular tribes. He
divides the CLASS of ANIMALCULA INFUSORIA as follows: Animal-
cule.
Genus 1. Monas; body punctiform. 10 species.
2. Proteus; body variable. 2 species.
3. Volvox; body spherical. 12 species.
4. Enchelis; body cylindrical. 27 species.
5. Vibrio; body elongated. 31 species.
6. Cyclidium; body oval. 10 species.
7. Paramacium; body oblong. 5 species.
8. Kolpoda; body sinuous. 16 species.
9. Gonium; body angular. 5 species.
10. Bursaria; body excavated. 5 species.
11. Cercaria; smooth, tailed. 22 species.
12. Trichoda; haired or ciliated. 89 species.
13. Kerona; with horny appendices. 14 species.
14. Himantopus; with ciliated appendices. 7 species.
15. Leucopha; the entire surface ciliated. 26 species.
16. Vorticella; orifice ciliated. 75 species.
17. Brachionus; orifice ciliated. 22 species.
In the year 1815 Lamarck published the first part of his Animalcules sans Vertèbres, a work which forms an epoch in the history of the inferior tribes. In this signal publication the author adopts a different course from that usually followed by systematic writers; and pursuing an ascending rather than a descending scale, he commences with the lowest and least complex species, viz. the Infusoria. From this class, however, he rejects all those species in which any kind of complication of organs is apparent. All the genera so distinguished are referred by him to the first order of the second class of the animal kingdom, called POLYPI, under the title of Polypi ciliati; and the true and restricted Infusoria are thus defined: Microscopical animals, gelatinous, transparent, polymorphous, contractile; having no distinct mouth, nor constant, determinable, internal organs; generation fissiparous or sub-gemmiparous. The genus Kerona, it may be further remarked, is in this system united to the Himantopus of Müller, while the genus Cercaria of that author is divided into two. Thus the class Infusoria of Lamarck, composed of two great sections, the naked and the appendiculated, may be said to correspond to the first 14 genera of the Danish naturalists.
Cuvier, in the Règne Animal (1817), places the Infusoria as a part of his fourth great division, the zoophytical or radiated animals. The term radiated was originally bestowed on a numerous tribe of animals, such as the Asterias and others, on account of their arms or tentacula being extended in a radiated or star-like form; but it certainly applies unfitly to the true Infusoria of Lamarck, which possess nothing resembling a radiated structure. It cannot, however, be always expected that a general term of wide import should apply with etymological accuracy to every part of the extensive series which it is intended to embrace. Cuvier then divides his Infusoria into two orders, Les Rotifères, and Les Infusoires homogènes, the former of which correspond to the ciliated polypi of La-
Animal-
cule. marck, the latter to the Infusoria properly so called of that author.
According to M. de Blainville, the class Infusoria can scarcely be regarded as established upon a natural foundation. The organization of its component tribes is so various as to lead to the belief that a more precise knowledge would show that several of those tribes belong to different types of the animal kingdom. Some, as the genus Brachionus, are symmetrically formed both as regards their bodies and appendages, and are protected by a horny or crustaceous covering. Others, as Vibrio, Paramæcium, &c. have the body elongated, depressed, vermiform, and without appendages. A third division exhibit a radiated structure, as for example the Vorticellæ, which, however, we have already stated, are now seldom classed among the Infusoria. Many genera, such as Proteus, Volvox, Monas, are amorphous, or without determinate form, and cannot be referred to any other known type of the animal kingdom. They are regarded by many as the elementary molecules of all animal life, and in their structure no other than the cellular tissue is observable. They may be said to be dependent on external circumstances, instead of being able, like other animals, to modify or control them; and their usually spherical form is the necessary result of an equal pressure of water on all sides of a frail and yielding texture. M. de Blainville considers the genera Brachionus, Ureclaria, Cercaria, Furcularia, Kerona, Trichocerca, and Himantopus, as belonging to the type of Entomozoaires or articulated animals, and especially to the class Heteropoda, order Entomostacea. Many species of Vibrio he regards as Apodes, as well as Paramæcium and Kolpoda. Other species of the genera Vibrio and Cyclidium ought rather to be ranged with the Planaria; and in the genus Leucopha there is even a species which M. de Blainville is inclined to look upon as an Ascidia! Finally, the genera Gonium, Proteus, Volvox, and Monas, if they are really animals, appear to form a distinct type, which may be called Amorphes or Agastaires; so named from the circumstance of their having neither determinate form nor reduplication of the external envelope for the formation of a stomach, as in all other true animals.
Such is a brief exposition of the views of one of the most distinguished physiological inquirers of the present day. It may serve, if for nothing more, at least to show the unsettled state of opinion concerning these extraordinary creatures. In regard to this, however, we may rest assured that, in the future progress of science, the class Infusoria, as at present constituted, will suffer an entire dismemberment, and its component parts will be referred to various groups of the animal kingdom, some of them widely distant from each other.
In the year 1826 a full and most elaborate classification of microscopical animals was given to the world by M. Bory de St Vincent. As it is the singular mode of existence of animalcular beings, their general economy in the field of nature, the actual conditions of their organization, and the state of their limited faculties so far as these can be ascertained, with which we are chiefly interested—so, in our systematic view of this extraordinary class, we shall merely present to our readers the characters of the principal genera, and of a few of the most remarkable species which they contain. But, as some may be desirous to possess at least a sketch of the full extent and condition of this intricate subject, we have constructed the accompanying tabular scheme of the orders, families, and genera of microscopical animals, according to the views of M. Bory de St Vincent, the latest and most assiduous writer on this department with whose labours we are acquainted. We have thought it advisable to retain the
terms of the original language, lest, by inadvertence or misconception on the part of the translator, any additional obscurity should rise around a subject already sufficiently encumbered. (See Tabular View on the next page.)
The order Gymnodes of Bory de St Vincent nearly corresponds to the entire class Infusoria of Lamarck; and although the observations by which he illustrates his arrangement partake of the accustomed defects of the French philosophy, the facts which he details, if not the theoretical views which he inculcates, are worthy of an attentive consideration. These mysterious creatures are observed to swim with astonishing rapidity; and although their bodies are usually diaphanous, it has hitherto proved impossible, even by the aid of the most powerful glasses, to ascertain by what natural mechanism these movements are effected. They direct their courses by a discretionary power, in one direction rather than another, avoiding and turning round opposing obstacles, according to the necessities of the case—discerning, as the process of evaporation proceeds, the points in which they may prolong their existence, and flocking in crowds to those places where they are best screened from the overpowering brilliancy of the reflecting mirror. They thus appear to possess volition, which we are accustomed to regard as a result dependent on the faculties of perception and comparison.
The principal obstacle to our understanding the essential nature of animalcules results from their want of a nervous system, which, in ourselves, and in all the intermediate classes of the nature of whose consciousness we have even a vague idea, we regard as the sine qua non of sensation and intelligence. Voluntary motion without muscular action is also a circumstance which we cannot very clearly comprehend. But as there may be "more things in heaven and earth than are dreamt of in our philosophy," we must not reject facts, that is to say appearances which present themselves under the same determinate and uniform aspect to various unprejudiced observers, merely because they do not coincide, or may possibly controvert or interfere, with a previous hypothesis. On the other hand, the extreme softness of texture, and excessive minuteness, of most of the animalcular species, render anatomical investigation almost impossible; and naturalists may have erred in supposing the absence of what they are merely unable to perceive and demonstrate.
It is in truth impossible to discover any traces of the nervous system, even among several tribes of animals in other respects much more highly organized than the subjects of our present inquiry. Trembley's examination of the Polypus threw no positive light upon the matter; nor did Gade's dissections of the larger Medusæ enable him to discover either muscular or nervous fibres. According to M. Bory de St Vincent, the nervous system is one of the last to be developed. To the perfect simplicity of the Monads, the first perceptible addition is that of a central cavity, or rudimentary intestinal sac, which we find to occur even before the existence of a mouth. Next appears an opening to this canal, which serves both for the reception of nourishment, and the rejection of excrementitious parts where such exist. The hairs and ciliated appendages which ensue in still more complicated species have been regarded as the early rudiments of the respiratory system; and even a heart, or central organ of a circulating fluid, is partly developed before the appearance of any nervous chords. The earliest, most general, and perhaps the only indispensable function of animal life, is that of nutrition. But the materials of nutrition are so different, and their modes of reception so various, that the exercise of this
TABLE OF THE ORDERS, FAMILIES, AND GENERA OF ANIMALCULES, according to a new Analytical Method. By BORY de SAINT-VINCENT.
| MERCOSCOPIQUES. | ORDRES. | FAMILLES. | GENRES. | ||||
|---|---|---|---|---|---|---|---|
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps anguleux, non articulés. | 1. Leucolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 2. Leptolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 3. Leptolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 4. Oligolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 5. Dendrolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 6. Dendrolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 7. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 8. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 9. Ectolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 10. Ectolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 11. Tricholysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 12. Tricholysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 13. Anopoda. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 14. Anopoda. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 15. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 16. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 17. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 18. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 19. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 20. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 21. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 22. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 23. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 24. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 25. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 26. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 27. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 28. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 29. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 30. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 31. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 32. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 33. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 34. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 35. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 36. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 37. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 38. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 39. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 40. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 41. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 42. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 43. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 44. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 45. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 46. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 47. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 48. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 49. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 50. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 51. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 52. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 53. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 54. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 55. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 56. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 57. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 58. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 59. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 60. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 61. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 62. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 63. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 64. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 65. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 66. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 67. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 68. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 69. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 70. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 71. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 72. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 73. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 74. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 75. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 76. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 77. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 78. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 79. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 80. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 81. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 82. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 83. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 84. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 85. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 86. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 87. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 88. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 89. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 90. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 91. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 92. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 93. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 94. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 95. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 96. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 97. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 98. Peripatolysa. | ||||
| Sans aucune apparence de test. | Sans aucune apparence de test. | Parfois sans glabre, sans cils ni cirres vibratiles... GYMNODÉS. | Jambes blanches ni anguleuses. | De forme plus ou moins variable. | Moléculaires toujours isolés, et formant autant d'individus. | Corps arrondi, jamais anguleux. | 99. Peripatolysa. |
| De forme plus ou moins variable. | Moléculaires groupés, et comme formant un individu en commun. | Corps arrondi, jamais anguleux. | 100. Peripatolysa. | ||||
Animal-
cule. function by no means necessitates the existence of a mouth, a stomach, or an alimentary canal; for an increase of parts may be effected even through the medium of imponderable or elastic fluids, and by imperceptible and superficial pores.
The exterior of an infusory animal may be compared to the interior of one of the higher classes, in which nutrition is carried on by the reception of the chyle by the absorbent pores. These pores are external among the Infusoria, and the process of absorption is with them analogous to that of plants, in which there is a direct reception and appropriation of fluids from the earth and air, without any previous preparation in a central cavity or stomach. Zoophytes in general have indeed been called the cryptogamia of the animal kingdom. According to Carus, the Infusoria ought to be regarded merely as little cells, partially filled with lymph, and possessed of the powers of nutrition and locomotion; and thus the infinite changes and variations perceptible in their forms may be supposed to be produced by the various degrees in which this fluid is collected at one or other of the points of their bodies. In the opinion of that anatomist, a more complete development of the organs of motion, and indeed of the whole organization, is inseparably united with the appearance of a distinct nervous system. This may be true as a general rule, but not as a universal principle; for the Medusa has more apparent voluntary motion than the Asterias, though the former is destitute of those nerves which in the latter make their first appearance in the shape of a pale thread-like ring surrounding the œsophagus. It is this ring around the upper extremity of the alimentary canal which, in the molluscous and articulated classes, we shall afterwards find to constitute the most uniform and most essential portion of the nervous system. The Medusa, just referred to, being almost of the same specific gravity with water, are easily carried by currents, and moved about from place to place by the action of the waves, or even (as in the case of Holothuria physalis) by the winds; but Carus and other writers have assuredly erred in doubting that they execute a voluntary locomotion; for that they do so in a very decided and graceful manner must be obvious to all who have attended to these animals in their native haunts along the shores, or among the land-locked waters of the beautiful firths of Scotland.
The mysteries revealed by the glasses of Leeuwenhoek were at first regarded as beyond belief. The uncertainty of microscopical investigations, in consequence of which so much was supposed to depend on the imagination of the beholder, was alleged against them; and even at an after-period, when men of sober judgment and the most industrious application had confirmed the experience of the indefatigable Dutchman, the wit of Voltaire did not disdain to throw its cutting sarcasm over the disciples of the "anguilles de la pâte et du vinaigre." We hope it is now admitted, that however frequently those who endeavour to expound the mysteries of nature may fail in their attempts at elucidation, yet that there is nothing in the manifold works of Omnipotent Wisdom which, if duly studied and rightly understood, would not conduce to our wellbeing and happiness; and that a single square inch of water, with its many millions of animalcular atoms, is in truth as wonderful a work of divine intelligence, and as interesting a field for human investigation, as the starry galaxy of heaven.
In his tam parvis, atque tam nullis, quæ ratio!
Quanta vis! quam inextricabilis perfectio!
And if a heathen philosopher (Pliny) has so expressed his
almost reverential admiration, is it not to be deplored that those whose labours might be carried on under the influence of a purer light, seem as often degraded as exalted by the contemplation of their Creator's works; and, referring all to the powers of nature, or some other indefinite abstraction, refuse to recognise, amid so many wonders, the "Good Supreme" from whom these and other mightier wonders have proceeded? It is in the study of the subject with which we are now engaged, and the analogous pursuits of physiology, where the completion of the most perfect design and the happiest results of superhuman forethought are so constantly manifested, that we frequently meet, where we should least expect it, with the sneer of the sceptic, or the impious ridicule of the unbeliever. How different are the sentiments of one who combines the piety of the Christian with the genius of the poet and philosopher. "But about the time of its invention (the invention of the telescope), another instrument was formed, which laid open a scene no less wonderful, and rewarded the inquisitive spirit of man with a discovery which serves to neutralize the whole of this argument. This was the microscope. The one led me to see a system in every star; the other leads me to see a world in every atom. The one taught me that this mighty globe, with the whole burden of its people and of its countries, is but a grain of sand on the high field of immensity; the other teaches me that every grain of sand may harbour within it the tribes and the families of a busy population. The one told me of the insignificance of the world I tread upon; the other redeems it from all its insignificance; for it tells me, that in the leaves of every forest, and in the flowers of every garden, and in the waters of every rivulet, there are worlds teeming with life, and numberless as are the glories of the firmament. The one has suggested to me, that beyond and above all that is visible to man, there may lie fields of creation which sweep immeasurably along, and carry the impress of the Almighty's hand to the remotest scenes of the universe; the other suggests to me, that within and beneath all that minuteness which the aided eye of man has been able to explore, there may be a region of invisibles; and that, could we draw aside the mysterious curtain which shrouds it from our senses, we might then see a theatre of as many wonders as astronomy has unfolded, a universe within the compass of a point so small as to elude all the powers of the microscope, but where the wonder-working God finds room for the exercise of all his attributes, where he can raise another mechanism of worlds, and fill and animate them all with the evidence of his glory."
Although we cannot hope to derive the same amusement or advantage from the study of each of the animalcular species considered separately, as we do from the consideration of the history of many of the higher animals, yet, in a philosophical point of view, a knowledge of the general attributes of the class presents several highly important objects; and their obscure origin, their singular organization, and more singular mode of existence, cannot fail to excite our unfeigned wonder and admiration. They can scarcely be described otherwise than by a negation of all those characters which constitute the life, power, and activity of other beings; they have no head, no eyes, no muscles, no blood-vessels, no nerves, no determinate organs for respiration, generation, or digestion—and yet they are endowed with life.
The animal nature of the Infusoria has indeed been denied by many; but such is the regular gradation from the most simply organized of the monadal forms to the much
more complicated structure of the Polypi, which present, under a remarkable aspect, such unequivocal characters of animality, that it is impossible to draw the line of demarcation; and if we admit the life of the one we can scarcely doubt that of the other. Yet many of the Infusoria appear to present the very lowest conceivable point to which animal life can be reduced.
The structure of an animal, the individual existence of which is preserved by the absorption of a circumambient fluid, and the continuance of whose species is effected by the division or separation of a part of its own body, might, a priori, be supposed to be of the most simple kind. "We may rest assured," observes Lamarck, "that whenever an organic function is itself unnecessary, the special organ by which it is usually performed will not be found to exist." It is indeed by considering the nature of the Infusoria that we are enabled to form a proper idea of the simplest condition of animal life; and the invention of the telescope was not of higher importance to the astronomer, than that of the microscope to the physiological naturalist. There are few subjects of reflection more interesting than the uses which philosophers of an enlightened age have deduced and matured from the scanty knowledge of a barbarous people. Glass, a material known at an early period to the Asiatic nations, and once estimated at its weight in gold, has become in the hands of Europeans of more value than the finest gold. Whoever polished the first lens may be said to have laid the foundation of an instrument destined to discover thousands of celestial worlds above and around us, and an unseen world of wonders beneath our feet. "Indeed," says Cuvier, "it could not be expected that those Phœnician sailors who saw the sand of the shores of Bœtica transformed by fire into a transparent glass, should have at once foreseen that this new substance would prolong the pleasures of sight to the old; that it would one day assist the astronomer in penetrating the depths of the heavens, and in numbering the stars of the milky way; that it would lay open to the naturalist a miniature world as populous, as rich in wonders, as that which alone seemed to have been granted to his senses and his contemplation; in fine, that the most simple and direct use of it would enable the inhabitants of the coast of the Baltic Sea to build palaces more magnificent than those of Tyre and Memphis, and to cultivate, almost under the frost of the polar circle, the most delicious fruits of the torrid zone."
The faculties of the most simple infusory animals, it has been observed, are reduced to such as are common to all living beings, and to that irritability which results from their animal nature; and their bodies are destitute of special organs, precisely because their extremely limited faculties neither require nor admit of such organs being exercised. The chief interest to be derived from the study of this class of beings results, according to Lamarck, from the view with which such study presents us of the ultimate point to which the organization of an animal is capable of being reduced; and, among all the wonders of the creation, he regards as the most surprising the existence of animal life in such inconceivably frail and simple bodies as the least complicated of the animalcular species. It is not, however, to be said that "nature was incapable of forming special organs from the materials of these frail gelatinous bodies," but rather that the all-wise Author and Ruler of Nature has seen fit to form them in what to us may appear a destitute and incomplete condition, merely because their structure does not fulfil those other conditions which, erroneously, we
have sought to establish as the indispensable bases of animal life. They truly show how confined a knowledge of our limited faculties enable us to gain of His unlimited power; for they not only present no analogy to other more accustomed forms of life, but almost seem to exist in direct opposition to those laws in accordance with which we "live, move, and have our being."
Infusory animals, commonly so called, are found in the fresh and saline waters of all countries. They occur both naturally, if we may use the term in a contradistinctive sense, and as the apparent result of infused animal and vegetable substances. According to Leeuwenhoek, the milt of a cod-fish contains more animalcules than there are individuals of the human race existing on the face of the earth; and he calculated that 10,000 might be held within the bulk of a grain of sand. The size of many bears the same relation to that of a mite as the dimensions of a bee do to those of an elephant; and the most powerful microscopes frequently discover nothing more than merely perceptible points in motion. Flour and water made to the consistence of book-binders' paste, exposed in an open vessel, and frequently stirred to prevent the surface from growing hard, will in a few days be found to contain millions of animalcules. The thin pellicle which grows on the surface of an infusion of common black pepper also produces an innumerable congregation of minute beings. Of these and others the real origin is still exceedingly obscure; and both Müller and Spallanzani maintained the improbable opinion that they fell from the air. Their subsequent increase or multiplication is obviously effected in different and very singular ways. Such as are spherical are usually propagated by minute portions, which, though they burst from the anterior of the animalcule itself, cannot be called eggs; and such as are of a depressed or flattened form continue their race by cuttings or divisions of their own bodies. We first observe a line or groove, longitudinal or transverse, according to the species; and ere long a notch or incision is perceptible at one or other or both of the ends of that apparent line. This notch increases across or longitudinally, till at last a portion is separated or cut off, or the original animal is divided into two, and each assumes the form and nature of their mutual predecessor. These new objects retain for some time their natural shape, and then in their turn give rise to one or more individuals by a similar separation of parts. Lamarck seems to be of opinion (Philosophie Zoologique, tome ii. p. 120 and 150) that this multiplication by division, and that by the emission of gemmules or oviform portions, are modifications of one and the same natural process;—that substantially each is the result of an extension and separation of parts, which take place when the parent individual has reached the final term of its increase. It is in fact the same excess of nourishment and growth of particular parts that, even in the higher classes, give rise to the germ of separate life, physically considered, although in regard to these the additional process of fecundation is required. It is the new light which may be gathered from the observation of the minutest of the animalcular tribes that renders their study both interesting and important to the physiologist; and it is the belief of some, that a persevering study of the history of microscopical animals will one day enable us to withdraw the mysterious veil which still conceals from our view the most important secrets of nature.
The systematic arrangement of animalcules which we propose to follow in this place is nearly that of Lamarck,
Animal- which is itself founded on the systems of Müller and cule. Bruguière. The French naturalist includes in his system only such species of the same class described by Müller as are destitute of a mouth.
Body extremely simple, apparently homogeneous, unprovided with organs or external appendages.
The naked Infusoria are the smallest and simplest of those animals which are cognizable by the senses of man. When we expose water to air and light, especially if it contains an infusion of animal or vegetable remains, we speedily perceive, by the assistance of the microscope, a variety of animalcules. These are divided into two sections.
Of this section the bodies present such a perceptible degree of thickness as removes them from the simply membranous state.
GENUS MONAS.—Body extremely small, of the simplest construction, transparent, punctiform.
The Monads are the smallest and least organized of living creatures. We have indeed scarcely any proof of their animal life, except that they are moving corpuscles, allied to the genus Volvox, the animality of which is undoubted. They have neither mouth nor alimentary canal, nor any apparent organs. They live by absorption, and are found in tranquil, but rarely in limpid waters. They are produced in infusions of animal and vegetable substances.
Sp. 1. Monas termo.—An extremely minute gelatinous point, scarcely perceptible even with the aid of a powerful lens, and frequently disappearing under a strong light in consequence of its perfect transparency. This species is common in ditch-water, and in numerous infusions. See Plate XLII. fig. 1. These minute creatures being the earliest discernible evidence of animal life, and the last result to which the higher and more perfect forms can be reduced by infusion, have been called the alpha and omega of all organized existence. Their history has given rise to many curious views, and more absurd speculations.
Sp. 2. Monas atomus.—White, with a variable dark-coloured spot, which appears to change its position. This species was found in sea-water which had been kept an entire winter, but was not very fetid. See Plate XLII. fig. 2 and 3.
Sp. 3. Monas punctum.—Nearly black, of a sub-cylindrical form. Found in the infusion of the pulp of a pear.
Sp. 4. Monas lens.—Hyaline, of an ovoid form. Found in all kinds of waters. Multiplies by spontaneous incision.
Sp. 5. Monas pulvisculus.—Hyaline, with a greenish margin. Found in the waters of marshes. This species has been lately regarded as an enchelis. Indeed, so great is the difficulty of microscopical investigation, and such indefatigable patience is required in order to see things as they really are, that the species and genera of this class of beings are frequently transposed and altered in their relative position and arrangement, in consequence of the very dissimilar views which different observers have taken of the same object.
As it would be inconsistent with our present limits to describe more than a few species of each genus, we shall content ourselves with the preceding Monads. "How many kinds," observes Mr Adams, "there may be of these invisibles, is yet unknown, as they are discerned of all sizes, from those which are barely invisible to the naked
eye, to such as resist the force of the microscope, as the fixed stars do that of the telescope, and, with the greatest powers hitherto invented, appear only as so many moving points."
GENUS VOLVOX.—Body very simple, transparent, spherical or ovoid, revolving on itself as on an axis.
With the exception of one species (V. globator) the volvices are invisible to the naked eye. Under the microscope they assume the aspect of small gelatinous masses, which sometimes present an oval form. In some the body seems composed of numerous smaller globules united in one common mass. There is reason to suppose that these interior bodies are afterwards propelled outwardly, and become separate individuals. The species occur both in fresh and salt waters, and in vegetable infusions. They derive their generic name from the manner in which they turn or revolve upon their axis. Leeuwenhoek describes an animalcule "a thousand times smaller than a louse's eye, which exceeded all the rest in briskness," and turned itself round as it were upon a point, with the celerity of a spinning-top. The genus is divisible into two sections.
* Interior of the body apparently simple and homogeneous.
Sp. 1. Volvox punctum.—Spherical, blackish, with a central lucid point. Of this species many are sometimes seen together in their passage through the water. They occasionally move as if subjected to the influence of a whirlpool, and then separate. Numerous in fetid sea-water.
Sp. 2. Volvox granulum.—Spherical, green, periphery hyaline. Dwells in the water of marshes.
Sp. 3. Volvox globulus.—Globular, sub-obscure behind. This species is ten times larger than the Monas lens. It occurs in most vegetable infusions, and moves with a slow fluttering motion. Plate XLII. fig. 4.
** Interior of the body exhibiting smaller corpuscles.
Sp. 4. Volvox pilula.—Spherical, with greenish internal globules. In those pure waters which nourish the Lemna minor. Plate XLII. fig. 5.
Sp. 5. Volvox lunula.—Roundish and transparent, and composed of an innumerable assemblage of homogeneous crescent-shaped molecules, without any common margin. Its movements are of two kinds, that of the molecules among themselves, and that of the whole revolving mass. It occurs in marshy places in the early spring. Plate XLII. fig. 6.
Sp. 6. Volvox globator.—Commonly called the globe-animal. Spherical, membranous, the internal globules distant or scattered. Abundant in the infusions of hemp and tremella, and in stagnant pools during spring and summer. The following is an account of it by Mr Baker. "There is no appearance of either head, tail, or fins, and yet it moves in every direction, backwards, forwards, up or down, rolling over and over like a bowl, spinning horizontally like a top, or gliding along smoothly without turning itself at all; sometimes its motions are very slow, sometimes very swift; and, when it pleases, it can turn round as upon an axis very nimbly, without moving out of its place. The body is transparent, except where the circular spots are placed, which are probably its young." Another authority states that this species is at first very small, but increases to such a size that it may be discerned by the naked eye, and that its interior is filled with small globules, which are smaller animalcules, each of which contains within itself a still smaller generation, all perceptible by means of powerful glasses. The lesser globules may be seen escaping from the parent, and increasing in size.
Animalcule. GENUS PROTEUS.—Body very small, simple, transparent, of varying form, changing itself instantaneously into different lobed shapes.
This genus is more obviously contractile than the preceding. It is seldom seen above a minute under the same form, but is continually passing from a simple oval or oblong to an irregular or sinuated shape, and vice versa. A species described by Roësel is so remarkable for this faculty, that it has been compared to a drop of water thrown upon oil. Hence also the generic name.
Sp. 1. Proteus diffuens.—Body diverging into branches. Occurs in the water of marshes. Plate XLII. fig. 7, 8, and 9.
Sp. 2. Proteus tenax.—Body prolonged to a fine point. Occurs in rivers and in sea-water. There are only two species described as belonging to this genus.
GENUS ENCHELIS.—Body very small, simple, oblong, cylindrical, slightly variable.
There is a marked analogy between this genus and the following. The Enchelides are, however, short and thick compared with the Vibriones, which are slender and lengthened. To the genus now under consideration belong those animals which, if the recorded observations on the subject have been accurately made and faithfully reported, more than any other confound our preconceived ideas regarding the distinction between animal and vegetable life. The species alluded to are named Zoocarpes by M. Bory de St Vincent, or animated seeds, which appear reciprocally to give rise to and proceed from certain aquatic plants of the conserve kind. They are formed in a bulbous-shaped part or swelling of the plant, are ejected when ripe, swim about for some time with a voluntary motion, throw out a root and a branch, become genuine vegetables, produce living seeds, and give birth to animals which, after a similar change of form, speedily return again to the vegetable state. These facts are vouched for by M. Bory de St Vincent, and are credited and confirmed by M. Dutrochet and several other continental inquirers, some of whom declare that they kept so watchful an eye upon the same individual as never to lose sight of it for a moment till they had witnessed the singular transformation above mentioned. We recommend it to our readers' consideration.
Sp. 1. Enchelis viridis.—Subcylindrical, obliquely truncated anteriorly. This species has an obtuse tail or terminal part. It continually varies its motion, turning from right to left. Occurs in long-kept water.
Sp. 2. Enchelis punctifera.—Subcylindrical, green, obtuse anteriorly, pointed posteriorly. This species is opaque, with a small pellucid spot in the fore part, in which two black points are seen, and a kind of double band crosses the middle of the body. It occurs in marshes. Plate XLII. fig. 10, 11.
Sp. 3. Enchelis pulvisculus.—This species bears a great resemblance to the Monas pulvisculus of Müller, which is the E. monadina of Bory de St Vincent. It is, however, double the size, deeper tinted, and more ovoid. It is found in the waters of marshes, and accumulates around the sides of jars or vases in which conserve have been kept. It forms on the surface of water a slight pellicle of a delicate green colour, which is supposed to have been erroneously regarded by many botanists as a vegetable production, and described under the name of Byssus flos aquæ. On dying it becomes more lengthened and pellucid, or at least retains only a slight central spot of green. Plate XLII. fig. 12.
Sp. 4. Enchelis amava.—This is a new species, of a lively green colour, discovered by Bory de St Vincent. In swimming it appears to elongate itself, and advances with
the more slender end foremost. Two individuals are sometimes observed to unite and form one animal, of a perfectly spherical form, and similar in aspect to a Volvox.
Sp. 5. Enchelis tiresias.—This species was also discovered by the above-named writer, and led to his peculiar views regarding those apparently animated seeds which he has named Zoocarpes. He asserts that he has seen this animalcule formed in the articulations of a true conserve; that it burst from its vegetable envelope with a gyration or circular movement; that it soon produced a translucent prolongation of its body, which may be called anterior, as it then swam in the direction of that new organ, which, with the body itself, became visibly longer, till the creature finally acquired the exact form of the Enchelid deses of Müller. The chief difference seemed to be that it always moved with the slender end foremost, whereas the species just mentioned swims with its blunt end in advance. It is described by recent French writers as an "animal extraordinaire qui n'est certainement que la grain vivante d'un végétal." (See Dic. Class. d'Hist. Nat. tome vi. p. 156.)
Sp. 6. Enchelid deses.—This species is of an obscure green, much elongated, and moves with the thick end anteriorly. "Celui-ci (the obtuse portion) paraît comme tronqué dans certains aspects; et en examinant attentivement cette sorte de troncature, on la reconnaît formée par un cercle en forme de disque moins foncé que le reste de l'animal. La pointe postérieure est parfaitement hyaline. Dans la pensée où nous sommes que les Enchelides vertes ne sont que des Zoocarpes, ou propagules animés de quelques genres d'Arthrodices, nous croyons que le disque obscurément transparent de la partie antérieure n'est que la marque du point sur lequel doit se développer l'article par lequel doit s'allonger en filament conservoide le Zoocarpe, lorsque, arrivé au terme de sa carrière animale, il doit se fixer et prendre racine par le point hyalin de la partie postérieure." (Loc. cit. p. 157.) We present the above passage to our readers without note or comment, as we do not ourselves understand the zoocarpal nature of an Enchelid.
GENUS VIBRIO.—Body very small, simple, cylindrical, elongated.
Animalcules have been described as constituents of this genus, which probably do not at all belong to it, being too complicated in their structure. If the V. aceti, for example, commonly called the vinegar eel, is furnished with a mouth, lips, and alimentary canal, it does not even pertain to the class Infusoria, however small its dimensions. But many of the species are undoubtedly of the simplest construction; and although they may present some appearance of an internal cavity or sac, they yet exhibit neither mouth nor other external orifice of any kind.
Sp. 1. Vibrio lineola.—Body linear, extremely minute. Occurs in many vegetable infusions in such numbers as apparently to occupy their entire space. It is so small, that with the best magnifiers little more can be discerned than an obscure tremulous motion. It is supposed to exceed even the Monas termo in tenuity. Plate XLII. fig. 13.
Sp. 2. Vibrio spirillum.—Filiform, and twisted spirally, which seems to be its natural shape, as it is never observed to unbend, but moves forwards with a vibratory motion at both ends. Found in an infusion of Sonchus arvensis. Plate XLII. fig. 14.
Sp. 3. Vibrio vermiculus.—Presents a milky aspect, with a blunt apex, and moves with a languid vermicular motion. It has been found in marshy water in November, but is seldom seen. It agrees with the animal mentioned by Leeuwenhoek as occurring in the dung of frogs.
Sp. 4. Vibrio pazillifer.—"Animalculum," says Müller.
Animal-cule. ler, "vel congeries animalculorum mirabilis. Pluries in guttulis aque marine vidi corpuscula linearia flavescentia (solitaria paleas, in quadrangula disposita scobes referent), granulaque seminalia qualiscunque vegetabilis diu credidi; demum nocte inter 6 et 7 Octobrem 1781 aspectu filii flavescentis, sese in longum producentis et in breve contrahentis, ac ex his paxillis compositi, obstupescens, novoque phenomeno gavisus, ejusdem variis evolutionibus incubui." A salt-water species, abundant in ulva latissima. Observed during the months of September and October. Plate XLII. fig. 15, 16, 17, 18, 19.
Sp. 5. Vibrio serpens.—Slender and gelatinous, with obtuse windings or flexures, resembling a serpentine line. It is rare, and occurs in river-water.
Of scarcely perceptible thickness, whether flat or concave.
The organization of the animalcules of this section is scarcely less simple than that of the preceding; but their form, being in a small degree resistant, is less subject to variation from the pressure or other action of the surrounding fluids, which has been regarded as the proof of a certain progress or advance in the scale of structure.
GENUS GONIUM.—Body very small and simple, flattened, short, angular. Some species of this genus appear to be composed of several corpuscles united together under a common membrane. This appearance probably results from their cellular tissue, or from certain lines which are the rudiments of those spontaneous divisions formerly mentioned, by which their propagation is affected. Their movements are oscillatory.
Sp. 1. Gonium pectorale.—Quadrangular and pellucid, with sixteen globules of a greenish colour set in a quadrangular membrane, "like jewels in the breast-plate of the high-priest, reflecting light on both sides." Occurs in pure waters. Plate XLII. fig. 20.
Sp. 2. Gonium pulvinatum.—Quadrangular and opaque. Found in dunghills.
Sp. 3. Gonium corrugatum.—Sub-quadrangular, whitish, marked by a longitudinal line. This species is found in various infusions, particularly that of the pear.
Sp. 4. Gonium truncatum.—Internal molecules dark green. Anterior extremity forming a straight line, with which the sides produce an obtuse angle, terminated posteriorly by a curved line. This species exhibits a languid motion. It is much larger than the preceding, and occurs, though rarely, in pure water.
GENUS CYCLIDIUM.—Body very small and simple, transparent, flattened, orbicular or oval.
The motions of this genus are oscillatory, circulatory, or demi-circulatory, more or less interrupted, and languid or lively, according to the species.
Sp. 1. Cyclidium bulla.—Orbicular and hyaline. General appearance pale and pellucid, with the edges somewhat darker than the rest. It moves slowly in a semicircular direction, and occurs in the infusion of hay.
Sp. 2. Cyclidium hyalinum.—Oval, depressed, perfectly transparent, terminated by a tail-like elongation. This species is very common, and is produced in many infusions, particularly in those of the cerealia. It swims in a vacillating manner, and as if continually trembling. Plate XLII. fig. 21.
Sp. 3. Cyclidium Nucleus.—Of a brownish tinge, deeper behind, and shaped exactly like an apple pippin.
GENUS PARAMÆCIUM.—Body very small, simple, transparent, membranous, oblong.
The species of this genus, according to Lamarck, scarcely differ from those of the preceding, except in their more
lengthened forms and a slight increase of animal development. They appear to vary instantaneously according to their position in relation to the eye of the observer; but their real form is tolerably determinate. The mode of increasing the species by transverse and longitudinal divisions, or natural cuttings, is very obvious in this genus. They are nearly related to the following, but are less sinuous and irregular. Their movements are for the most part slow and indefinite. They swim horizontally on one of their flattened surfaces, after the manner of flounders.
Sp. 1. Paramæcium aurelia.—Body compressed, with a kind of plait or fold towards the apex, acute behind. Very common in water where confervæ grow. Plate XLII. fig. 22, 23, 24.
Sp. 2. Paramæcium chrysalis.—Plicated anteriorly, obtuse behind. Occurs during the autumn in sea-water.
Sp. 3. Paramæcium versutum.—Cylindrical, thickened posteriorly, obtuse at both ends. Found in ditches.
GENUS KOLPODA.—Body very small, simple, flattened, oblong, sinuous, irregular, transparent.
This genus is nearly allied to the preceding, and differs from it chiefly in its more varied forms. It is also less subject to the influence of pressure by the medium in which it lives. An Italian naturalist of the name of Losana has lately published a monograph on Kolpoda; but his figures are somewhat exaggerated, and not very naturally expressed.
Sp. 1. Kolpoda lamella.—Elongated, membranaceous, curved anteriorly. This species is seldom met with. It has a singular vacillatory mode of movement, and advances on its sharp edge, instead of its flattened side, the more usual position.
Sp. 2. Kolpoda gallinula.—Oblong, the anterior portion of the back membranaceous and hyaline. In corrupted sea-water.
Sp. 3. Kolpoda crassa.—Yellow, thickish, somewhat opaque, curved a little in the centre, kidney-shaped. This species has a quick vacillatory motion, and becomes apparent in the infusion of hay generally in about 13 hours. When the water is nearly evaporated it assumes an oval form, becomes compressed, and bursts.
Sp. 4. Kolpoda rostrum.—Oblong, hooked anteriorly. The movements of this species are slow and horizontal. It is found, but not frequently, in water where the lemna grows.
Sp. 5. Kolpoda cucullus.—Ovate, ventricose, the top bent into a kind of beak, and an oblique incision beneath the apex. This species is found in vegetable infusions, and in fetid hay, and usually moves with great velocity. It is pellucid, and appears as if filled with little bright vesicles, which differ in size. Some have supposed them to be lesser animalcules which the Kolpoda has swallowed; but as it has no mouth wherewith to swallow, Müller is more probably right in regarding them in the light of germs. When about to die in consequence of evaporation, it protrudes its contents, whether food or offspring, with great violence. Plate XLIII. fig. 25, 26, 27, 28.
GENUS BURSARIA.—Body simple, membranaceous, concave.
This genus occurs in fresh, saline, and stagnant waters. It appears to vary its form beneath the eye of the observer, and, from a rounded flattened shape, assumes a concave or somewhat purse-shaped aspect.
Sp. 1. Bursaria truncatella.—Follicular, with a truncated apex. This species is visible to the naked eye. It moves from left to right, and from right to left; ascends to the surface in a straight line, and sometimes rolls about as it descends.
Sp. 2. Bursaria bulina.—Boat-shaped, labiated anteriorly. This species is pellucid and crystalline, with brilliant globules within it. It is concave on the upper side, and convex below.
Sp. 3. Bursaria hirundella.—With two small wing-like projections, which give it somewhat of the appearance of a bird. It is invisible to the naked eye, but appears under the microscope like a pellucid hollow membrane. Recent micrographical observers doubt if this species really pertains to the present genus. Plate XLIII. fig. 29.
Furnished exteriorly with projecting parts.
The animalcules of this second principal order or division, though still infinitely small, gelatinous, and transparent, are so far less simply organized than their predecessors, inasmuch as they are furnished with salient parts, such as hairs, horns, or tail-like appendages, or at least with such projecting organs as, for want of more appropriate terms, we are obliged to designate by those names. They multiply both by division and by the bursting forth of internal germs. Though their essential fluids, and the living tissue which contains them, are probably of a more compound nature than those of the naked Infusoria, they have not yet reached that point of organization in which special organs are developed for the performance of particular functions; and it is not till we reach the higher class of Polypi that these are distinctly perceptible.
"Il paraît," observes Lamarck, "par les nombreuses espèces déjà connues et publiées, que les Infusoires de cet ordre sont bien plus nombreux dans la nature que les Infusoires nus. Cela doit être ainsi d'après les principes que je me suis cru fondé à établir.
"En effet, dans les Infusoires nus, l'origine encore trop récente des races qui proviennent de celles, en petit nombre, qui furent générées spontanément, n'a permis à la durée de la vie et aux circonstances qui ont influé sur ces races, qu'une diversité peu considérable. Mais à mesure que la durée de la vie, que sa transmission dans les individus qui se sont succédé en se multipliant, et que les circonstances ont eu plus de temps pour exercer leurs influences, les races se sont diversifiées de plus en plus, et sont devenues plus nombreuses.
"Cet ordre des choses, qu'il est facile de reconnaître pour celui même de la nature, nous fait sentir pourquoi les Infusoires sont bien moins diversifiés et moins nombreux que les Polypes. Effectivement, quoique nous ne connaissions pas probablement tous les Infusoires, et que nous connaissions bien moins encore tous les Polypes, ce qui est déjà connu de part et d'autre indique que la diversité des Polypes est considérablement plus grande que des Infusoires. Aussi les Polypes sont plus éloignés de leur origine que les Infusoires." (Animalcules sans Vertèbres, tome I. p. 433.)
The first genus of this order (Trichoda), as constituted by Müller, contains several species which manifest the rudiments of a mouth and the commencement of an alimentary canal: these, according to the negative characters of the class, do not belong to the Infusoria.
GENUS TRICHODA.—Body very small, transparent, diversiform, without caudal appendage, but garnished with soft hairs either on the whole or on part of its surface.
According to the views of Lamarck, this genus contains not only a great proportion of the genus Trichoda of Müller, but also the whole of the genus Leucophra of the Danish author. It is distinguished from Kerona by the
want of the long, stiff, distant, corniform hairs which characterize the latter.
A. Body ciliated over its entire surface.
(Leucophra of Müller.)
Sp. 1. Trichoda viridiscens.—Greenish, cylindrical, opaque, thicker posteriorly. Found in sea-water.
Sp. 2. Trichoda dilata.—Body flattened, variable, with sinuated margins. Inhabits sea-water, and swims like a Planaria. It scarcely differs from the genus Kolpoda, except in being ciliated.
Sp. 3. Trichoda scintillans.—Of a green colour, oval, slender, and opaque. Occurs in stagnant water. A doubtful species, closely allied to Volvox.
Sp. 4. Trichoda acuta.—Ovate, with a sharpened point. Colour yellowish. Of this species the form is very variable. It occurs in sea-water among ulvæ. Plate XLIII. fig. 30, 31, 32.
Sp. 5. Trichoda signata.—Oblong, sub-depressed, with a blackish margin. Common in sea-water. This species is distinguished by a curved line in its centre, shaped like the letter S, one end of which sometimes assumes a spiral form.
Sp. 6. Trichoda mammilla.—Spherical, opaque, with an exsertile papilla. Occurs in the waters of marshes. It is of a dark colour, its short hairs are curved inwards, and it occasionally appears to project and draw in a little white protuberance.
B. Body ciliated, or covered with short hair only over a part of its surface.
(The greater proportion of the genus Trichoda of Müller.)
Sp. 7. Trichoda grandinella.—Spherical, pellucid, haired above. The minute ciliary appendages of this species are not easily discovered, as it seems to possess the power of withdrawing them at pleasure and instantaneously. It occurs both in pure water and that of infusions.
Sp. 8. Trichoda cometa.—Spherical, ciliated anteriorly, with one or more globular appendages behind. Found in pure water in the autumnal season. Plate XLIII. fig. 33, 34.
Sp. 9. Trichoda solaris.—Spherical and crystalline, its edges beset with diverging rays, which exceed in length the diameter of the body. This animalcule contracts and dilates, but is stationary in the same spot. In marine infusions. Plate XLIII. fig. 35.
Sp. 10. Trichoda pubes.—Oval oblong, gibbous, depressed anteriorly. The apex of this species is furnished with hairs, which are seldom visible till it is about to expire, when it protrudes and extends them vehemently, as if in a vain attempt to secure and detain a remaining particle of water.
Sp. 11. Trichoda proteus.—Oval, obtuse behind, with an elongated retractile neck. Apex haired. This species, according to Müller and Lamarck, is found in river water. It appears, however, to agree in general character and appearance with the Proteus described by Mr Baker, which usually occurs in the slimy matter adhering to the sides of vessels in which either animal or vegetable substances have been some time kept. That of which an account is given by Mr Adams was found in the slime produced by water containing small fishes, snails, &c. The body was something similar to that of a snail, but pointed at one end, while from the other proceeded a long, slender, "and finely proportioned neck, of a size suitable to the rest of the animal." If we credit Mr Baker, this animalcule, though its eyes are not discernible, plainly demonstrates by its actions that it can see; for though multitudes swim about in the same water, and its own progressive motion is
Animal- very swift, it never strikes against its neighbours, but di-
cule. rect its course with a dexterity "wholly unaccountable should we suppose it destitute of sight." Its entire shape bears a resemblance to that of a swan. See Plate XLIII. fig. 36 and 37. When alarmed, it draws in its supposed neck, becomes more opaque, and moves about slowly with the large end foremost. See fig. 38. After continuing for some time under this form, it will put forth a kind of wheel machinery, the motions of which are alleged to draw a current of water towards it from a considerable distance. After frequently pushing out and pulling in this shorter head, sometimes with and sometimes without the wheel-work, it will remain motionless, as if wearied or worn out; and then its long head and neck or apex will be again slowly protruded, after which it generally resumes its accustomed agility.
GENUS KERONA.—Body very small, diversiform, without tail-like prolongation, and furnished with scattered, stiff, corniform hairs on some parts of its body.
To this genus Lamarck has united the Himantopus of Müller. The species are rare. They seldom occur in infusions, and are most frequent in the purer kinds of fresh and salt waters.
Sp. 1. Kerona rostellum.—Orbicular and membranaceous; one side angulated, the other furnished with a series of triple horns. Inhabits sea and river water. This species is alleged by Bory de St Vincent to be entirely destitute of hairs and cirri, and he therefore proposes to remove it to the order Gymnodes, which corresponds with our first order, the naked Infusoria. It is sometimes difficult to identify species in this department, or to ascertain, in a doubtful or contested case, that the same animalcule has been the subject of observation by two or more disputants. Plate XLIII. fig. 39.
Sp. 2. Kerona cypris.—Somewhat pear-shaped, compressed, the front furnished with hairs or vibrating points, inserted beneath the edge, shorter behind, and partly extended straight forward, partly bent downwards. Motion retrograde. Inhabits fresh water.
Sp. 3. Kerona ludia.—Smooth, pellucid, full of small points, the fore part clubbed and a little bent, the hinder part narrow; the base obliquely truncated, and terminating in a tail stretched out transversely. The top of that part which may be called the head, and the centre of the back, are furnished with long hairs. When this animalcule is at rest, its tail is curled; when in motion it is drawn tight and extended upwards. The movements of this species are lively and diverting.
GENUS CERCARIA.—Body very small, transparent, diversiform, furnished with a distinct but very simple tail.
This genus, as constituted by Müller, contains many species which bear no natural relation to each other; but his characters are precise and definite, and strictly applicable to those species which now form the genus as limited by modern observers. They occur more rarely among animal and vegetable infusions than in running streams and the waters of marshes. Their movements are for the most part circular and very rapid. With the exception of a well-marked tail, their organization is in every other respect extremely simple. If a mouth and the rudiment
of a stomach or alimentary canal exist in any of these animals, such characters would remove them not only from the genus Cercaria, but from the class Infusoria, as defined at the commencement of this treatise. A fortiori, the existence of eyes (a fact assumed by some inaccurate observers) in any of the animalcular species, would entirely alter their position and arrangement in the animal kingdom. We cannot do better than report the observations of the venerable Lamarck (himself unfortunately now deprived of sight) on this obscure subject:—"Ici, comme dans le genre suivant, l'on est exposé, d'après la petitesse extrême des individus, à rapporter à la classe des Infusoires des animaux qui, par leur organisation, appartiennent à d'autres points de l'échelle animale."
"Une bouche, quoique d'abord inaperçue, et conséquemment l'ébauche d'un sac alimentaire, peuvent exister dans certains de ces animaux, et dès-lors ils appartiennent au premier ordre des Polypes; mais des yeux, comme on en a supposé dans certains Cereaires, cela est impossible."
"Avant de dire que le fait lui-même vaut mieux que la raisonnement, il faut, 1mo, constater que les points que l'on a pris pour des yeux, en sont réellement, et qu'ils ont chacun un nerf optique qui se rend à une masse médullaire, centre de rapports pour des sensations; 2do, il faut ensuite établir positivement que des animalcules réellement pourvus d'yeux, sont néanmoins, par leur organisation, de la même classe que les Infusoires." (Animalcules sans Vertèbres, tome i. p. 444.)
This genus forms the nucleus of the new family of Infusoria proposed by M. Bory de St Vincent under the name of Cercariées, and which contains in all seven genera, the names and nature of which will be seen by referring to the tabular view. Müller, who was not practically acquainted with the spermatid animalcules, was attracted by the resemblance which some of the Cercariae bore to the figures of those organic molecules in the works of his predecessors. He did not, however, assert their identity; and probably perceived that, although in their general aspect and mode of movement they resembled each other, their peculiar and very different localities, and even the details of their structure, rendered it advisable that they should be assigned to separate genera.1
Sp. 1. Cercaria inquieta.—Changeable, convex, with a slender tail. This species occurs in salt water, and is remarkable for assuming a variety of different forms. It is sometimes oval, sometimes cylindrical, sometimes shaped like a sphere. Plate XLIII. fig. 40.
Sp. 2. Cercaria gyrinus.—Body of a rounded form, with an acuminate tail. In swimming, this animalcule moves its tail like a tadpole.
Sp. 3. Cercaria lemna.—Changeable, sub-depressed, with an annulated tail. The C. lemna varies the form of its body in a manner almost as singular as that exhibited by the Proetus, already described. The body is triangular, or oblong, or kidney-shaped. Its tail is at times thick, short, annulated; at others it is long, cylindrical, and without rings; and when stretched out it sometimes vibrates with such velocity as to appear double. A small pellucid globe, which Müller regarded as the mouth, is perceptible near the apex; and there are also two excessively minute black points, which, whatever they may really be, are by some called eyes. It advances slowly by a few steps or movements at a time, and frequently shakes and bends its tail, in which position it bears a great resemblance to a
1 The following are the characters of the genus Zooperna, as recently established: "Corps non contractile, ovoïde, très-comprimé, avec une queue setiforme, aussi longue ou beaucoup plus longue, implantée à la partie postérieure, qui est peu ou point amincie. Ce genre, dont nous possédons un très-grand nombre d'espèces, se compose d'animaux spermatiques." (Dict. Class. d'Hist. Nat. tome iii. p. 356.) The production and existence of these animals, their nature and uses, are still among the many inscrutable mysteries of nature.
Animalcule. lemma leaf in miniature. This animalcule exhibits an advanced organization. Plate XLIII. fig. 41, 42, 43.
GENUS FURCOCERCA.—Body very small, transparent, rarely ciliated, furnished with a bipartite tail.
This terminal genus, according to the views of Lamarck, conducts us to the limits of the infusorial class, and we become thus more liable to deception in regard to the non-existence of a mouth than in the preceding genera. It is a dismemberment of the Cercaria of Müller, and probably contains many species which will be placed elsewhere when future and more continuous observation shall have thrown additional light upon their nature and attributes.
Sp. 1. Furcocerca podura.—Cylindrical, acuminated posteriorly. This species is pellucid, and seems to consist of a head, trunk, and tail, the first of which, in the view of some observers, "resembles that of a herring." It turns round as if upon an axis when it moves, and is usually found in the months of November and December, in places where the lemma abounds. The tail frequently, but not always, appears to be divided into two. One of Müller's figures of this species is probably erroneous. He represents it as covered with short hairs; whereas, to more recent observers, it appears perfectly smooth. Plate XLIII. fig. 44, 45.
Sp. 2. Furcocerca viridis.—Cylindrical, variable, divided and acuminated behind. Occurs in spring in ditches and standing pools. It frequently contracts its anterior and posterior portions, so as to assume a spherical form. It is difficult to determine the genus to which this species belongs. Lamarck is supposed to have erred in placing it where it now stands. In truth, the genus appears to have been rather established provisionally, than upon an assured and natural foundation. The varying forms of the species which it contains render it extremely difficult either to discern or describe them with precision. Plate XLIII. fig. 46, 47, 48.
We have now endeavoured to present a general view, and a systematic exposition, of the principal features of the animalcular world; and if our statements have been less explicit, and our arrangement less complete and methodical, than accords with the reader's expectation, these defects must in part be attributed to the uncertainty which still prevails regarding a subject of which many of the essential characters scarcely lie within the limits of human intelligence. The observations and experiments of the English microscopical observers of last century, though they might amuse the general student, are too vague and fanciful to be now regarded as parts of the assured history of animalcules. The ultra-analogical reasoning on subjects of natural science with which we have been lately favoured by such men as Oken and Geoffroy St. Hilaire, are tame in comparison with the inferences deduced by some of our older observers, who describe with minuteness the head, eyes, mouth, jaws, throat, stomach, intestines, and other parts of animalcules, which the improved glasses of modern times do not reveal to the vision of not less patient inquirers. The recent observations on the motions of the pollen of plants, which have puzzled the modern philosophers, would have opposed but feeble barriers in the way of our predecessors. "To discover," says Buffon, "whether all the parts of animals, and all the seeds of plants, contained moving organic particles, I made infusions of the flesh of different animals, and of the seeds of more than twenty different species of vegetables; and after remaining some days in close glasses, I had the pleasure of seeing organic moving particles in all of them. In some they appeared sooner, in others
later; some preserved their motions for months, and others soon lost it. Some at first produced large moving globules resembling animals, which changed their figure, split, and became gradually smaller; others produced only small globules, whose motions were extremely rapid; and others produced filaments, which grew longer, seemed to vegetate, and then swelled and poured forth torrents of moving globules." It was from these and similar observations that the theory arose proposed by Baron Munchausen (an ominous name!). The Baron perceiving that these moving globules, after taking a little exercise, began again to vegetate, drew the conclusion that they were first animals and then plants; thus anticipating by more than half a century the supposed discoveries of some modern physiologists. Which of them was first in error it is perhaps of little consequence to inquire; and we allude to the subject here rather in connection with some singular observations by Mr Ellis, recorded in the 59th volume of the Philosophical Transactions, than from its own intrinsic importance. His object was to overturn Munchausen's hypothesis, by showing that the supposed Zoo-carpes were nothing more than "the seeds of that genus of fungi called mucor or mouldiness," and that their motions were caused by the attacks of myriads of animalcules! "Having at the request of Dr Linnæus made several experiments on the infusion of mushrooms in water, in order to prove the theory of Baron Munchausen, that these seeds are first animals and then plants, it appeared evidently that the seeds were put in motion by very minute animalcules, which proceeded from the putrefaction of the mushroom: for by pecking at these seeds, which are reddish, light, round bodies, they moved them about with great agility in a variety of directions; while the little animals themselves were scarcely visible till the food they had eaten had discovered them. The satisfaction I received from clearing up this point led me into many other curious and interesting experiments. The ingenious Mr Needham supposes these little transparent ramified filaments, and jointed or coralloid bodies, which the microscope discovers to us on the surface of most animal and vegetable infusions when they become putrid, to be zoophytes, or branched animals; but to me they appear, after a careful scrutiny with the best glasses, to be of that genus of fungi called mucor or mouldiness, many of which Michellius has figured, and Linnæus has accurately described. Their vegetation is so amazingly quick, that they may be perceived in the microscope even to grow and feed under the eye of the observer. Mr Needham has pointed out to us a species that is very remarkable for its parts of fructification (See Phil. Trans. vol. xlv. tab. 5, fig. 3, a, A). This, he says, proceeds from an infusion of bruised wheat. I have seen the same species proceed from the body of a dead fly, which was become putrid by lying floating for some time in a glass of water where some flowers had been, in the month of August 1768. This species of mucor sends forth a mass of transparent filamentous roots; from whence arise hollow stems, that support little oblong oval seed-vessels, with a hole on the top of each. From these I could plainly see minute globular seeds issue forth in great abundance, with an elastic force, and turn about in the water as if they were animated. Continuing to view them with some attention, I could just discover that the putrid water which surrounded them was full of the minutest animalcula; and that these little creatures began to attack the seeds of the mucor for food, as I have observed before in the experiment on the seeds of the larger kind of fungi or mushrooms. This new motion continued the appearance of their being alive for some time longer; but soon after many of them arose to the surface of the water, remaining there without
Animal-
cule. motion: and a succession of them afterwards coming up, they united together in little thin masses, and floated to the edge of the water, remaining there quite inactive during the time of observation." In like manner, the movements of the jointed coralloid bodies which Mr Needham has named chaplets and pearl necklaces are attributed to the attacks of their animalcular enemies. "When a small portion of these branches and seeds are put into a drop of the same putrid water upon which the scum floats, many of these millions of little animalcula with which it abounds immediately seize them as food, and turn them about with a variety of motions, as in the experiments on the seeds of the common mushrooms, either singly, or two or three seeds connected together; answering exactly to Mr Needham's description, but evidently without any motion of their own, and consequently not animated!"
We shall conclude this subject with a short notice of another view of the matter, which has resulted from some recent experiments and observations by our celebrated botanist Robert Brown. While engaged in some inquiries regarding the structure of the pollen of plants, and its mode of action on the pistillum of phenogamous tribes, that accurate observer had occasion to immerse in water some particles taken from the full-grown anthers (previous to bursting) of Clarkia pulchella. Of these, he perceived by the microscope that many were evidently in motion, and that their motion consisted not only of a change of place in the fluid, but of a change of form in themselves; that is to say, a contraction or curvature about the middle of one side, accompanied by a corresponding enlargement or convexity on the other, frequently occurred. The particles were seen, in a few instances, to turn on their longer axis; and their general motions were of such a nature as to produce the conviction in Mr Brown's mind that they did not arise either from currents or evaporation of the fluid, but were proper to the particles themselves. Having ascertained that motion existed in the pollen of all the living plants which he examined, he next inquired whether, and for what length of time, this singular property was retained after the death of the plant. Specimens were experimented on, which had been dried and preserved in an herbarium for 100 years, and the moving molecules or small spherical bodies were still perceived in considerable numbers. "The very unexpected fact," says Mr Brown, "of seeming vitality retained by those minute particles so long after the death of the plant, would not perhaps have materially lessened my confidence in the supposed peculiarity; but I at the same time observed, that on bruising the ovula or seeds of Equisetum, which at first happened accidentally, I so greatly increased the number of moving particles, that the source of the added quantity could not be doubted. I found also, on bruising first the floral leaves of mosses, and then all other parts of those plants, that I readily obtained similar particles, not in equal quantity indeed, but equally in motion. My supposed test of the male organ was therefore necessarily abandoned. Reflecting on all the facts with which I had now become acquainted, I was disposed to believe that the minute spherical particles or molecules of apparently uniform size, first seen in the advanced state of the pollen of Onagraceæ, and most other phenogamous plants,—then in the antheræ of mosses, and on the surfaces of the bodies regarded as the stamina of Equisetum,—and, lastly, in bruised portions of other parts of the same plants,—were in reality the supposed constituent or elementary molecules of organic bodies, first so considered by Buffon and Needham, then by Wrisberg with greater precision, soon after and still more particularly by Müller, and very recently by Dr Milne Edwards, who has revived the doc-
trine, and supported it with much interesting detail. I Animal-
cule. now, therefore, expected to find these molecules in all organic bodies; and accordingly, on examining the various animal and vegetable tissues, whether living or dead, they were always found to exist; and merely by bruising these substances in water, I never failed to disengage the molecules in sufficient numbers to ascertain their apparent identity in size, form, and motion, with the smaller particles of the grains of the pollen. I examined also various products of organic bodies, particularly the gum raisins, and substances of vegetable origin, extending my inquiry even to pit-coal; and in all these bodies molecules were found in abundance. I remark here also, partly as a caution to those who may hereafter engage in the same inquiry, that the dust or soot deposited on all bodies in such quantity, especially in London, is entirely composed of these molecules. One of the substances examined was a specimen of fossil wood, found in Wiltshire oolite, in a state to burn with flame; and as I found these molecules abundantly and in motion in this specimen, I supposed that their existence, though in smaller quantity, might be ascertained in mineralized vegetable remains. With this view, a minute portion of silicified wood, which exhibited the structure of coniferæ, was bruised, and spherical particles, or molecules in all respects like those so frequently mentioned, were readily obtained from it; in such quantity, however, that the whole substance of the petrification seemed to be formed of them. But hence I inferred that these molecules were not limited to organic bodies, nor even to their products. To establish the correctness of the inference, and to ascertain to what extent the molecules existed in mineral bodies, became the next object of inquiry. The first substance examined was a minute fragment of window-glass, from which, when merely bruised on the stage of the microscope, I readily and copiously obtained molecules, agreeing in size, form, and motion, with those which I had already seen. I then proceeded to examine, and with similar results, such minerals as I either had at hand or could readily obtain, including several of the simple earths and metals, with many of their combinations. Rocks of all ages, including those in which organic remains have never been found, yielded the molecules in abundance. Their existence was ascertained in each of the constituent minerals of granite, a fragment of the sphinx being one of the specimens examined. To mention all the mineral substances in which I have found these molecules would be tedious; and I shall confine myself, in this summary, to an enumeration of a few of the most remarkable. These were both of aqueous and igneous origin, as travertine, stalactites, lava, obsidian, pumice, volcanic ashes, and meteorites from various localities. Of metals I may mention manganese, nickel, plumbago, bismuth, antimony, and arsenic. In a word, in every mineral which I could reduce to powder sufficiently fine to be temporarily suspended in water, I found these molecules more or less copiously; and in some cases, more particularly in siliceous crystals, the whole body submitted to examination appeared to be composed of them."
There were three points of importance which Mr Brown was anxious to ascertain regarding these molecules, viz. their form, whether they were of uniform size, and their absolute magnitude. He seems, however, not to have been entirely satisfied with his determination on any of these points. As to form, he states the molecules to be spherical. His manner of estimating the absolute magnitude and uniformity of size of the molecules found in the various bodies submitted to examination, was by placing them on a micrometer divided to five thousandths of an inch, the lines of which were very distinct; or, more rare-
Animal-cule. ly, on one divided to ten-thousandths, with fainter lines, not readily visible without the application of plumbago, as employed by Dr Wollaston, but which in this case was inadmissible. The results can only be regarded as approximate, but Mr Brown is disposed to believe that the molecule is of uniform size, though, as existing in various substances, and examined in circumstances more or less favourable, he regards it necessary to state that its diameter appeared to vary from th to th of an inch.1
Since the preceding exposition of animalcules was written, great and important additions have been made to our knowledge of the subject. Both the organic structure and the physiological functions of these creatures have been described at great length, and amply illustrated, by Ehrenberg of Berlin. We are deeply indebted to that author for much that he has achieved in an obscure and difficult department,—for his general views, not less than his detailed descriptions,—and especially for the influence which he has shown many animalcular beings to have exercised, by means of their siliceous remains, in the building up, as it were, of various geological formations. At the same time it must be borne in mind, that many of Ehrenberg's discoveries have been much contested, and that Dujardin and other recent writers do not accept his classification, in consequence of what they deem its hypothetical basis. In presenting the views of the first-named observer, we therefore do so under a sense of the critical correction which others have sought to bestow upon them, and of which we shall also in our present supplement endeavour to give a brief account.
The following is a summary of Ehrenberg's views of the general character and attributes of infusorial beings.
They are all organized,—the greater portion (probably all of them) highly organized bodies.
They constitute two very natural classes (Polygastrica and Rotatoria), according to their structure, and are further subdivisible upon the same principle.
Their existence in all quarters of the earth and sea, is proved; as is also that of individuals of the same species in the most opposite ends of the world.
Their geographical distribution upon the earth follows the laws observed as regulating that of other natural bodies.
Most of the Infusoria are invisible to the naked eye; many are just visible as moving points; the size of the body does not in any case exceed th of an inch.
Invisible Infusoria, in consequence of their vastly aggregated numbers, colour large tracts of water with remarkable hues.
Though themselves invisible, they also give rise, in consequence of this aggregation, to a certain kind of marine phosphorescence.
They sometimes compose, though singly invisible, a kind of mould, very obvious in consequence of the multitudinous mass. In a single cubic inch of this mould, there may be above 41,000 millions of animalcules; and they probably constitute the chief proportion of living bodies on the face of the earth.
They are the most reproductive of all organized beings; and from one of their known modes of propagation, that of self-division, ensues a continual destruction of the individual, and yet a similar interminable preservation and extension of it, in air and water, bordering, it may be almost said, upon eternal life and growth.
The copulation of gemmæ, which perhaps includes the hitherto unsolved poly-embryonate riddle of the seeds of all plants and vegetable formations, is solved in the animalcular family of Closterina.2
They form in the course of time, in consequence of the enduring nature of their siliceous shells, indestructible earths, stones, and rocky masses.
With lime and soda we can prepare glass and swimming bricks out of invisible animalcules; we can use them as flints, and probably prepare iron from them; we use mountain meal, which is composed of them, as food in hunger.
They are sometimes injurious, by causing the death of fish in ponds, deteriorating clear water, and causing boggy smells; but they do not, as some have supposed, give rise to malaria, plague, and other maladies.
They appear to be, as far as yet known, sleepless.
They partially break up in reproduction (egg-laying), and thereby passively undergo great alterations of form.
They form invisible intestinal beings in man and other animals, even if the Spermatzoa are excluded from among them. They are themselves infected by both external and internal parasites.
1 The following summary from the pen of Mr Brown contains the renewed expression of that gentleman's opinion, matured by some recent experiments on the subject of active molecules. "That extremely minute particles of solid matter, whether obtained from organic or inorganic substances, when suspended in pure water or in some other aqueous fluids, exhibit motions for which I am unable to account, and which, from their irregularity and seeming independence, resemble in a remarkable degree the less rapid motions of some of the simplest animalcules of infusions. That the smallest moving particles observed, and which I have termed Active Molecules, appear to be spherical, or nearly so, and to be between th and th of an inch in diameter; and that other particles of considerably greater and various size, and either of similar or of very different figure, also present analogous motions in like circumstances. I have formerly stated my belief that these motions of the particles neither arose from currents in the fluid containing them, nor depended on that intestine motion which may be supposed to accompany its evaporation. These causes of motion, however, either singly or combined with others,—as the attractions and repulsions among the particles themselves, their unstable equilibrium in the fluid in which they are suspended, their hygrometrical or capillary action, and in some cases the disengagement of volatile matter, or of minute air-bubbles,—have been considered by several writers as sufficiently accounting for the appearances. Some of the alleged causes here stated, with others which I have considered it unnecessary to mention, are not likely to be overlooked, or to deceive observers of any experience in microscopical researches; and the insufficiency of those enumerated may, I think, be satisfactorily shown by means of a very simple experiment. This experiment consists in reducing the drop of water containing the particles to microscopic minuteness, and prolonging its existence by immersing it in a transparent fluid of inferior specific gravity, with which it is not miscible, and in which evaporation is extremely slow. If to almond oil, which is a fluid having these properties, a considerably smaller proportion of water, duly impregnated with particles, be added, and the two fluids shaken or triturated together, drops of water of various sizes, from th to th of an inch in diameter, will be immediately produced. Of these, the most minute necessarily contain but few particles, and some may be occasionally observed with one particle only. In this manner minute drops, which, if exposed to the air, would be dissipated in less than a minute, may be retained for more than an hour. But in all the drops thus formed and protected, the motion of the particles takes place with undiminished activity, while the principal causes assigned for that motion, namely, evaporation and their mutual attraction and repulsion, are either materially reduced or absolutely null."
2 Among other difficulties with which the student of this department will have to contend is the following,—that many species classed by Ehrenberg and others as animalcules, are considered by botanists as pertaining to their particular kingdom. Thus the Desmidiaceæ, a great component group of Ehrenberg's family Basillaria, are viewed by Professor Bailey of New York as belonging to the vegetable kingdom. Among ourselves, Dr Harvey, so noted for his knowledge of marine plants, classes both these and the Diatomaceæ, as sub-orders of the Chloropermeæ, or green Algae. Mr Ralfs, who has written so excellent a monograph on the "British Desmidaceæ," likewise regards these as Algae. It is indeed a vexed question as to the animal nature even of the Diatomaceæ, which, by means of genera, such as Melosira, and others, seem closely connected with the confervoid Algae.
Animal- They possess comparatively a lengthened life.
cule. As the pollen of pine trees falls yearly in the form of sulphur-rain, so do the much more minute animalcules appear (being elevated by means of watery vapour) floating alive in the atmosphere, and sometimes even mixed with dust.
They generally, like the more highly-organized bodies, maintain themselves pretty uniformly against all external influences. Although they sometimes consume strong poisons without immediate injury, they do not do so without an after effect.
The weight of invisible Infusoria, although light, is calculable, and the most gentle current of air or draught can play with their bodies as with the vapour of water.
The obvious and very rapid motion of Infusoria, is reducible as follows:—Hydatina senta moves 1-12th of an inch in 4 seconds; Monas punctum, the same in 48 seconds; while Navicula gracilis takes 6 minutes 24 seconds to go the same distance.
Linnaeus said, omnis calc e vermicibus: either to maintain or deny omnis silex omne ferrum e vermicibus would now be unjust.
Direct observations on the theory of generatio primitiva are wanting in necessary strictness. Those who profess to have seen the sudden origin of the minutest Infusoria from elementary substances, have quite overlooked the compound structure of these organic bodies.
The frequent and wonderful changes of form of many Infusoria no doubt have their limits, although the laws which govern them are still to be defined.
The power of infusorial organization is exhibited by the strong chewing apparatus, with teeth, which they possess, and their exhibition, also, of a complete mental activity.
The study of the Infusoria has led to a more distinct and conclusive notion of animal organization in general, and of the limits which circumscribe the animal form; from which all plants and minerals, which want the animal organic system, are strongly and distinctly separated.
It finally results from these inquiries, that experience shows an unfathomableness of organic creations, when attention is devoted to the smallest space, as it does of stars when directed to distances the most immense.
It was the prevailing opinion, till of later years, that the generality of animalcules were devoid of external organs; but the use of coloured substances, and the introduction of achromatic glasses have certainly shown a much more composite structure than was formerly known to exist. The simplest member is a delicate filament, placed near the oral orifice, and therefore called the proboscis. When the animalcule is in motion, this proboscis seems to act as a sort of oar or paddle, while, at the same time, by creating a current in the direction of the mouth, it aids in the prehension of food. Cilia are shortish hairs, placed apparently upon a bulb. They vibrate rapidly, the hair turning round upon something like an articulated surface, while the points describe a comparatively large circle. These cilia show themselves remarkably among the Rotatoria, in the shape of wheels, and both in form and action may be regarded as among the most interesting spectacles presented by the animalcular world. Naturalists are somewhat divided regarding their functions. Many look upon them as organs of respiration, and there is no doubt that corresponding parts are placed around the gills of many mollusca, and bring to them currents of fresh water for the purposes of breathing. Of the existence of eyes in the animalcular world we are still extremely doubtful, when we consider the fact of their non-existence in great groups distinguished in all other respects by a more complex and complicated organization. In Müller's great work no eyes are represented
in any of the Polygastric species, but certain specks containing a red pigment have been assumed as eyes by Ehrenberg; and he argues that even if no other proof of the existence of a nervous system in these animated atoms could be adduced, the visual spots referred to would be sufficient to prove it. Having, as he supposes, discovered visual organs in these red specks of the Rotatoria families, he argues from analogy that the same parts perform similar functions in the Polygastric groups. M. Valenciennes maintains that in the Rotatoria these eye-specks are distinctly defined, have an investing capsule, and a crystalline lens, and consequently possess the essential attributes of organs of sight. On the other hand, owing to the extreme minuteness of the Polygastric species, all appearance of definite outline is wanting in their red specks, and as similar characters occur upon the reproductive germs of Algae (which belong to the vegetable kingdom), their necessarily visual character is denied by many considerate observers.
"The sense of sight," says M. Dujardin, "would partake more of the character of a reality if the colour of a speck without appreciable organization, without a constant form, or a precise contour, sufficed to prove the existence of an eye. But in the genus Euglena, which is particularly cited as characterized by such an organ, the red spot so regarded is excessively variable, sometimes multiple, at other times made up of irregularly aggregated granules. Analogy, too, is inadequate to the solution of the question; for, on descending the animal series, to determine the nature of this coloured speck, we have to leap from the Daphniae (an Entomostracal tribe) with a moveable eye, repeating in its composition that of Insects and Crustacea, to animals presenting nothing but diffused coloured specks.
"Such spots, whether in number or position, have so little physiological importance in the Planaria, and in certain Annelides, that they are often not even to be employed as an absolute specific character. In the Rotatoria, the analogy with which is more especially insisted on, these pigment spots are, in some species, known to disappear from age, and in others to become more evident in proportion to size or development of individuals: so that the learned micrographer of Berlin, in his attempt to base the generic characters of these animals on the presence and number of eyes, has been led to place in different genera, species very closely allied, if not identical. Indeed, that a black or a red colour is in general an attribute of the pigment of eyes, cannot be a reason for concluding an eye to exist wherever we find such colours; if so, we must accord it to some intestinal worms, such as the Scolex polymorphus, which has two red spots on the neck, to the Actinia, which are often strewed with such specks, and also to some bivalved mollusks.
"If the ability of the Infusoria to direct their course through the liquid, and to pursue their prey, be appealed to in evidence, it is certainly, in the first place, necessary to verify the reality of this faculty, which I think equally fabulous with all related concerning the instincts of these animals. Indeed it would not even prove the red specks to be eyes, since the greatest number of Infusoria supposed to be endowed with such a faculty are in want of them; and those which do possess them do not exhibit that power in any higher degree of development."1
In the opinion of M. Morren, the red pigment specks of Lagenella, Cryptoglena, and Trachelomonas, cannot be eyes, because in the last-named genus the coloured pigment is capable of being distributed over the whole body, in which case, according to Ehrenberg's supposition, the creature itself would be converted into nothing but an eye.2
Professor Owen observes, in relation to the movements of Polygastric animalcules, that although they may be per-
1 Histoire des Infusoires.
2 Mém. de l'Acad. de Bruxelles, 1841, taf. 14.
ceived to avoid obstacles in their way, and rarely jostle one another, it is yet difficult to detect any definite cause or object of their movements.1 After carefully watching for signs of volition, that great observer came to the conclusion that those movements partook in general of the nature of respiratory acts, rather than of attempts to obtain food or avoid danger. They seemed automatic rather than voluntary, as if governed by stimuli within or without the body, not felt, but reflected upon contractile fibre, and are therefore motions which never tire. He thus explains the fact already indicated in our abstract of Ehrenberg's general views, namely, that at whatever period of the night we examine living Infusoria, we shall invariably find them as ceaselessly active as during the meridian splendour, and thus that animalcules never sleep.
The same unsettled state of opinion as regards the eyes, pervades our knowledge of other important parts of animalcular economy, and even the great basis (the assumed peculiarities of the digestive system) of Ehrenberg's classification being regarded as hypothetical, the classification itself has been by many rejected on that ground. According to the Berlin naturalist, the functions of digestion among the Polygastrica are effected by means of numerous internal vesicles or stomachs; while in the Rotatoria, as in the generality of higher animals, there is only one. While studying species of the former class, Ehrenberg observed a vesicle to fill with food, and then saw the particles pass into another cell, and so on until, the nutritive portions having been imbibed by each stomach in succession, the refuse was discharged by the animalcule. That many other naturalists have been unable to detect this process is perhaps no conclusive argument against it, as great experience, and the most steadfast and accurate observation, are necessary in microscopical pursuits. Few have been able to detect the tubular connection between these stomachic cells, which, however, must exist if Ehrenberg's views are well founded. He affirms that he has often seen it, and the passage is very distinctly shown upon his plates. Baron Gleichen regarded these vesicles as eggs, although he failed to witness their discharge; and the existence of eggs among the Polygastric tribes, is perhaps as much of an assumption as any other. So far back as 1781, he tried to make certain Infusoria eat carmine, and found on the ensuing day that several of them had red granules in their interior.2 He concluded that they had swallowed the colouring matter, and more recent repetitions of similar experiments led to the formation of Ehrenberg's system. Professor F. T. Meyen refuses to admit the facts on which it is founded, not only because he has failed to see the intestinal communication between the stomachs, but has observed these supposed stomachs moving rapidly in the interior of the body of many species, after the manner of those granules which circulate in the joints of Chara. He has often seen Vorticella with many globules of indigo in their interior, always moving round a centre; from which he infers there could not be a communicating canal between the so-called stomachs with an oral orifice, and an extremity directed towards the mouth. In regard to the true nature of these
vesicles, and balls of similar diameter, found in the bodies of Infusoria, Meyen is of opinion that the true Infusoria are themselves vesicular beings, the interior of which is filled with a mucous substance: the thickness of the membrane forming the vesicle is easily ascertainable in several species, and in many he has noticed in this membrane an obvious spiral structure, resembling that which exists among cellular vegetables. In the larger Infusoria, a cylindrical canal (the œsophagus) traverses obliquely the membrane which forms the animal. The lower extremity of this canal dilates, more or less, when the creature has taken food, until it attains the dimensions of the balls, which are so obvious in the interior of these Infusoria. The inner surface of this upper portion of the intestinal canal is provided with cilia, which turn round not only alimentary substances but foreign bodies, till they have assumed a spherical form. During the formation of this ball, the stomach, according to Meyen (who admits that the part in question must be distinguished by that name), has a free communication with the œsophagus; and by means of the ciliary apparatus found at its exterior, new alimentary substances are introduced into this canal, and pushed as far as the stomach. When the ball has acquired the dimensions of the stomach, it is expelled by its inner extremity, and pushed into the cavity of the body. It there forms an additional ball, if any solid substances had previously existed in the surrounding liquid. This second ball is itself pushed into the interior of the cavity of the animal, and drives before it the first ball along with the mucosities between the two—a successive formation of similar balls, by the food or other matter received into the animal, going on without interruption. Now, Meyen maintains that it is the simultaneous existence of many of these balls which has caused Ehrenberg to believe that these animalcules were Polygastric. To follow their formation, our observations must commence at the moment the animalcules are plunged into coloured liquid. The swallowing of the coloured particles takes place with great rapidity, frequently in half a minute, and the coloured balls may be seen one after another issuing from the stomach, and proceeding downwards along the internal wall of the cavity of the body. Their number is often so considerable as to fill the entire cavity, and they lie so close together as to form a large mass, which, as in the genus Vorticella, slowly turns upon itself. The vesicular cavities, according to Meyen, are not stomachs, and possess nothing in common with the balls, although the latter may get into them singly, but at the same time accidentally. The formation of these cavities, as well as their sudden and entire disappearance, may be traced as easily as the origin of the balls. It is even possible sometimes to see how one of these cavities moulds itself over a ball, and then disappears. The microscope reveals to us that they are not lined with a particular membrane, but are simply excavations of the pulpy substance. They often show themselves close to the inner surface of what forms the skin of the creature, and sometimes increase so greatly, that the diameter of even one is equal to the third or one-half of the entire cavity of the body.3
1 Comparative Anatomy and Physiology of the Invertebrated Animals, p. 19.
2 As the use of infusions is indispensable in the study of living microscopic objects, we extract the following notice of the method of feeding infusoria with coloured substances, from Mr Pritchard's work. Select for the purpose such coloured substances as are entirely free from metallic oxides, and not chemically soluble in water. They must, however, be capable of a very minute mechanical division. The substances generally used are carmine, indigo, and sap-green, the first being preferable. The material should be as pure as possible. Rub a piece of it once or twice on the stage glass, or what is better, the lower plate of an aquatic air-box, having first moistened it with a drop of water. The quantity of colour requisite is very small, no more than sufficient to render it appreciable by the naked eye; for if there be too much, the chances are that the particles will be too large for the creatures to imbibe. Having thus prepared the coloured food, place a drop of it beside a drop of water containing the animalcules, but not so near as that they may come in contact; then put gently on the cover of the air-box, and lower it sufficiently to flatten the two drops of fluid, but not to force them to unite. Now place the air-box under the microscope, and examine the animalcules closely, so as to ascertain that their stomachs are colourless; then press down the cover until the drops of fluid intermingle, which may be done under the microscope, and you will immediately perceive the creatures in great activity, and readily distinguish the cilia and proboscis of such as possess those parts, while in a few seconds their stomachs will be filled by the coloured substance.—See Infusorial Animalcules, p. 108. 2d Ed. 1852.
3 Edin. Phil. Jour., vol. xxviii.
Animalcule. According to Dujardin, the Infusoria (setting aside the Systolides or Rotatoria, as much higher in the animal scale, and also the Bacillaria, which, with Closteria, are more nearly related to the vegetable kingdom) derive their origin for the most part from obscure or unknown germs, in artificial and natural infusions, stagnant water, and rivers, or such portions of them as rest over vegetable remains; no other mode of propagation, except self-division, being well ascertained. Their fleshy substance is dilatable and contractile, like the muscular flesh of the higher animals, but it exhibits no absolute trace of fibres or membrane, seeming, on the contrary, to be homogeneous and diaphanous, except in cases where the surface appears articulated from contraction. This fleshy matter when isolated by tearing, or the death of the animalcule, shows itself in the liquid in the form of lenticular discs or globules, which refract light but slightly, and are capable of producing spontaneously in their substance spherical cavities analogous in appearance to the vesicles of the interior. In the living creature some of these vesicles are produced at the base of a sort of mouth, and are destined to contain the water swallowed with the aliments. They then pursue a certain course in the interior, and contract, and leave nothing in the centre of the fleshy substance, except the undigested particles. They can even discharge their contents externally by a fortuitous opening, which may be reproduced several times towards the same, though not the identical, point. The vesicles containing the aliment are independent, and neither communicate with an intestine, nor with each other, except in those cases where two vesicles incorporate. The other vesicles, which contain nothing but water, are formed much nearer the surface, and seem capable both to receive and expel their contents through the meshes of the integument. Spallanzani considered them as respiratory organs, and they may be so regarded, at least in so far as they multiply the points of contact of the interior substance with the circumambient fluid.
Dujardin is, moreover, of opinion in regard to the so-called eggs of Infusoria, their generative system, their organs of sense, their nerves and vessels, that none of these can be ascertained or determined with exactitude; and everything inclines him to believe that these minute creatures, although clearly endowed with a simple organization, according with their mode of life, cannot be regarded as possessing the same systems of organs as the higher tribes. The coloured points, for example, usually of a red colour, which have been regarded as eyes, cannot with propriety receive that appellation.1
Siebold is also opposed to the view that these vesicles or sacs are special and distinct digestive organs, and he denies the existence of any connecting canal. The Astoma (mouthless animalcules) he regards as nourished only by a general absorption of the surface. In the Stomatoda (those with evident mouths) he represents the oral orifice as continued into the interior by a sort of œsophagus, wide, and of very various form, terminating abruptly in the general loose parenchyma of the body. The food, when sought for, is drawn towards the mouth by the action of the surrounding cilia, and having been received into the mouth, enters the œsophagus, and is thence pushed onwards by a contraction of the part, in the form of a rounded globule, into the interior. After performing, during a sojourn there, a greater or less circuit, the food in the generality of Stomatoda is ejected through a fixed outlet, not, as Dujardin maintains, by means of a varying opening through the surface.
Wagner asserts that no one by any examination, however close, can convince himself of the actual existence of such an organization as Ehrenberg affirms. He maintains that in many Infusoria, where comparatively large bodies, such as
Navicula or joints of Alga, have been swallowed, no surrounding vesicle can be seen, and that these bodies will sometimes occupy the entire length and breadth of an animalcule. In the absence of mouth, nutrition seems carried on by the general surface. It may be safely inferred from these conflicting opinions that no settled or satisfactory conclusion can be formed, and that Ehrenberg's theory of polygastric structure, though it may be true, requires confirmation. The same may be said of several other organs and their functions. We have dwelt upon the digestive system at greater length than we shall do upon any other, as it forms the basis of Ehrenberg's arrangement of the animal kingdom.
In regard to the reproductive process among these infusorial tribes, Monas vivipara is regarded by Ehrenberg as the only species of the class that is viviparous. The formation of eggs, is considered by that author as a fertile and frequent source of increase. Dujardin, again, views the viviparous attributes of the above-named Monas as more than doubtful, and the formation of ova in any infusorial species as by no means ascertained. He considers Ehrenberg's instances of oviposition as examples merely of diffusion, or the breaking up of the gelatinous substance of the animalcule into spherical atoms from want of moisture. With Siebold, he limits the reproductive process in this class to the two forms of gemmation and spontaneous fission. If this be true, then all that has been written of the ovaries, vesiculae seminales, &c., falls to the ground. Professor Owen, however, is of opinion that the function of the nucleus of Infusoria in reproduction by spontaneous fission may be regarded as analogous to that of the essential contact of the Spermatozoon with the germ-cell in the development of the higher classes; and comparing the results in the two cases, he says it is certain "that the analogy between these phenomena in the multiplication of the parts of the germ-mass and those of the nucleus in the multiplication of monads is so close, that one cannot reasonably suppose that the nature and properties of the nucleus of the impregnated germ-cell, and that of the monad can be different." He therefore infers that the nucleus of the Polygastric animalcules is the seat of the spermatogenic power, though the term testes can only be figuratively applied; and he thinks that if Ehrenberg be correct in viewing the interstitial corpuscles as germ-cells, these essential parts of ova may receive the essential matter of the sperm from the nucleus, which is discharged along with them in the breaking up of the monad, which Ehrenberg regards as equivalent to an act of oviposition; and impregnated cells may thus, in Professor Owen's view, be prepared to diffuse through space, and carry the species of Polygastric animalcules to a distance from the scene of the life of the parent.2
Professor Weisse supposes himself to have detected reproduction by ova in Chlorogonium euchlorum, and maintains that the continuous observation of that species demonstrates that several of Ehrenberg's genera are nothing more than its natural development from stage to stage.3 He describes the green matter of chlorogonium as developing, by spontaneous fission of itself, numerous young animalcules, which at first resemble Uvella Bodo, and are afterwards converted into Chlorogonium euchlorum and Glenomorum tingens. What he calls oviposition is the escape of the young by a transverse rupture of the parent, which is itself sacrificed, and disappears as a shrivelled sack. But in conformity with Thuret's views, it may be doubted whether the organic being (we shall not say creature) were really an animalcule, and not merely a theca or zoospore (of an alga), a production which so resembles the green-coloured Infusoria that Mr Pritchard states we have no means of dis-
tinguishing between the two. It equally produces by the fission of its endochrome or green contents. M. Thuret has shown how close is the analogy between the reproductive bodies of Confervæ and those of the green animalcules. He regards the Tetraspore, although ranked with the Algae, as of very doubtful vegetable nature. The movements of the animalcular genus Diselmis resemble those of zoospores, and the species equally turn to the light, under the influence of which, like algae, they act upon the atmospheric air, disengaging a gas (oxygen?) when exposed to the rays of the sun. In a particular stage of one species, a very clear red spot was discernible, and a central globe closely resembling the amylose granules so common in the cells of algae. It is the prevalence of the coloured speck in Diselmis Dunalii which, according to M. Joly, is the chief cause of the red colour so frequently observed over a large space of water in the Mediterranean Sea.
Whatever may be the special mode of generative increase among animalcules, their vast and rapid accumulation is as undoubted as extraordinary. Even among the Rotiferæ, direct observation has shown that a single individual will give rise to one million in ten days, and to sixteen millions in little more than a fortnight. If the children follow the footsteps of the parent, it is not easy to say what another fortnight might produce. Among the Polygastrica, the increase is still more speedy, one million having been produced from a single individual in seven days. Good and substantial food is, however, an essential condition of this rapid development; and when we consider what minute mouthfuls must suffice, we may the more easily conceive how rich a provender is spread before them in those innumerable infusions of animal and vegetable matters contained in almost all liquids. Fuchs has made some curious observations on the animalcules of cow's milk. He there finds in abundance two monadal species. He states that the blueness of milk is owing to the development and increase of an infusorial being, which he calls Vibrio cyanogenus. Under the name of Vibrio xanthogenus he defines another species, which he alleges makes milk turn yellow. Ehrenberg is of opinion that, in accordance with certain laws of nature, "living organisms," such as animalcules, may be developed in the air. The region of atmospheric dust is of vast extent, and ascends above 14,000 feet; and he conceives that its phenomena cannot be traced to mineral matters from the earth, nor to materials floating in space, nor to atmospheric currents, but rather bear relation to some general law of our atmosphere, in accordance with which there is a development within it of living organisms. The quantity of actual matter of this kind which falls from the air upon our earth is enormous, in consequence of the vast surface which it covers, however thinly. Meteorolites, although comparatively solid and massive, are as nothing compared with it. It has been calculated, that of atmospheric stones there fell, from 1790 to 1819, 600 cwt.; whereas a single dust-shower, which was deposited at Lyons in 1846, is estimated at 7200 cwt. As these showers have been numerous over the whole earth, Ehrenberg asks, how many millions of tons weight of animalcular beings have fallen since the time of Homer? Important results have been deduced from the examination of the animalcular dust which falls at sea, as well as on land, in the determination of the direction of atmospheric currents.1
Whatever defects may exist in Ehrenberg's system of arrangement, in consequence of some fallacies in his mode of viewing the organic structure and physiological functions of these extraordinary beings, there is no doubt that we owe to him many important observations and discoveries. He has especially pointed out the great influence exercised by
these minutest of beings in the actual structure of the solid crust of the earth. He has satisfied both himself and others that the calcareous rocks of Syria and of Central North America contain densely crowded masses of small Polythalamiae, several species of which, from the limestone of the New World, are identical with those of the European chalk. He has found the plastic marl of Ægina to consist of organisms, several of which pertain to the animalcules of the chalk. Lüneberg Heath is described as a great bed of Infusoria; and one of the largest deposits yet known is near Berlin, in which it is remarkable that species still living, but not hitherto discovered at the surface of the soil, are found among the fossil species. Quekett has recorded that an infusorial stratum, twenty feet in thickness, underlies the city of Richmond in Virginia, and that several of the forms agree specifically with those found in the North Sea. Abundance of microscopic shields belonging to marine Infusoria (both the siliceous-shelled Polygastrica, and the calcareous-shelled Polythalamia) occur in the deposits of the Elbe, near Hamburg and Glückstadt. Similar results were yielded by the mud of the Scheldt, and by marine deposits on the shores of the North Sea and Baltic. Ehrenberg has well shown the enormous proportionate extent and intensity of life in the highest latitudes both north and south, and at the greatest attainable depth of the ocean.
So prodigious are the aggregations of these smallest forms of life, that they have actually raised, and are still raising, vast tracts of land from the bottom of the sea. Our antarctic voyagers have informed us that the waters of the ocean, between the parallels of 60° and 80° south latitude, are of a pale ochre-brown colour, in consequence of the enormous accumulation of these the frailest and yet least perishable parts of creation. Their death and decomposition have, we know not in the course of how long a period, actually produced a submarine bank or deposit of such vast dimensions, as to occupy an area of 400 miles long by 120 wide, flanking, as Dr. Joseph Hooker has informed us, the entire length of the Victoria Reef.
Among the more singular localities of the Infusoria may be mentioned, not only meteoric dust, already noticed, but volcanic ashes, and other precipitations from the atmosphere. Ehrenberg has also shown that the blood-red spots which, to the terror of the superstitious, sometimes appear on bread and other substances, are occasioned by the surprisingly rapid development of an animalcule called Monas prodigiosa. He further supposes that one of the miracles in Egypt, recorded by the great lawgiver of the Jews, of the turning of water into blood, was produced, humanly speaking, by means of Euglena sanguinea (Ascaria viridis of Müller, for it is sometimes green), or by the use of another species called Astasia hamatodes.
The character of the lorica, or somewhat shelly covering, differs in its nature and composition in the different genera; being in some entirely siliceous, in others, composed of lime, combined with carbonic acid as a carbonate, with a portion of the oxide of iron. As in many of the smaller genera it is difficult to ascertain whether they are enclosed in a lorica or not, we may here state Mr Pritchard's mode of ascertaining the existence of that character. Having obtained some specimens, say of the family Cryptomonas, he places a drop of water containing them in a compressor or crush-box, mixing a little colouring matter with the water. If the species are loricated, a clear transparent ring will be observed under the microscope, encircling the animalcules, and seeming to keep them separate from the fluid in which they are immersed.2 Should this test prove unsatisfactory or insufficient, then the cover of the box may be pressed down, so as to
1 A complete history of showers of meteoric dust will be found in Ehrenberg's Fastat-Staub und Blut-Regen, of which a brief abstract is given in Pritchard's Infusorial Animalcules, p. 89.
2 Infusorial Animalcules, p. 13.
crush the specimens, when the coloured fluid will enter and surround their bodies; and, by a proper and expert management of the illumination of the microscope, the broken edges of the lorica will become visible.
The unfixed condition of opinion regarding infusorial animalcules is curiously indicated by the fact, that many careful and assiduous observers, such as Bauer, Leuckhart, Agassiz, and Reichenbach, deny the very existence of these creatures as a class, and maintain that they are mostly the embryonic forms of other and more highly organized beings. We doubt not that the opinion expressed in our preceding article, that our knowledge of this "invisible world" is in its infancy, is still correct, and that as the telescope brings forth stars from their nebular darkness, so the further the light of our microscopic knowledge penetrates into the obscure depth of the animalcular kingdom, the more clearly we shall have its now component parts resolved into definite forms of another nature than we at present suppose them. But that they are all merely embryonic forms, is doubtless a most visionary view, as no reason can be assigned a priori that beings, however small, are either uncertain or transitional, or that completion and finality of form are in any way inconsistent with excessive minuteness. One lesson may assuredly be drawn from the difficulties which beset the subject, to avoid dogmatism, and bear in mind how unable we often are to solve the question, "What is truth?" But the extraordinary mutability of form and outward aspect of those frail creatures is no argument against their fixity of specific character within a certain range of variation, however wide. We know how different are the individuals even of some of the higher species from each other, under different circumstances, and at different stages of their life; but when once under our eye, they may be made cognizable to the senses of an observant person, under all their phases; that is, they may be identified with certainty from time to time. But with many animalcular beings it is not so. We see them once, as the astronomer may see some "bright particular star;" but we cannot calculate their erratic and changing course of life; and thus they may be either seen again no more for ever, or be observed under an altered aspect by another observer, and recorded with new characters under a different name. These, and such-like causes, may easily be conceived to operate disadvantageously against our speedy acquirement of assured knowledge regarding the animalcular tribes. But by means of patient and discriminating investigation on our own parts, a candid consideration of the observations of others, and an unbiased record of whatever has been clearly ascertained, there is no reason why the subject should not be gradually advanced so as to take rank with other branches of a less ambiguous nature. The general
reader will not wonder at the state of uncertainty which still pervades our notions of many animalcules, when we mention, as an example of extreme minuteness, Monas crepusculum, of which the number occupying the space of a grain of mustard seed, one-tenth of an inch in diameter, has been calculated at eight millions!
Ehrenberg's great group of polygastric animalcules is primarily divided into Anentera (such as do not possess a true alimentary canal), and Enterodela (or such as are furnished with an alimentary canal). Here we are met by a noted antagonistic observer upon the very threshold.
"Recent investigations," says M. Agassiz, "upon the so-called Anentera, have satisfactorily shown, in my opinion, and in that of most competent observers, that this type of Ehrenberg's Polygastrica, without gastric cavities, and without an alimentary tube, are really plants belonging to the order of algae in the widest extension of this group; while most of the monad tribe are merely moveable germs of various kinds of other algae. As for the Enterodela—most of them, far from being perfect animals, are only germs in an early stage of development. The family of Vorticella exhibits so close a relation with the Bryozoa (cilio-brachiate polypes), and especially with the genus Pedicellina, that I have no doubt, that wherever Bryozoa should be placed, Vorticella should follow, and be ranked in the same division with them. The terminal group of Infusoria, Bursaria, Paramoecium, and the like, are, as I have satisfied myself by direct investigation, germs of fresh-water worms, some of which I have seen hatched from eggs of Planaria laid under my eyes."1
Not only are authors on our present department opposed to each other, but (a rarer case) they seem in some instances to have no great confidence even in themselves. Thus M. Dujardin, one of the most trustworthy of the modern microscopic observers, after giving in a tabular form the characters of the groups which constitute the family Monadina, sums up by stating: "But these generic distinctions are entirely artificial, and simply intended to facilitate the naming of Infusoria one may meet with in such and such infusions, and which, when better known, may prove in some instances to be but varieties of a single species."2
The preceding notices will suffice to show the still unsettled state of opinion regarding animalcules, and that Ehrenberg's system, although of great importance to the discriminating student, is not to be adopted implicitly as an assured exposition of the truth. We cannot here exhibit more of his arrangement than a compendious view of the family groups, referring for details of genera and species to the work itself,3 and to others, with a list of which we shall conclude these supplementary observations.
| Family. | ||||||
|---|---|---|---|---|---|---|
| ANENTERA, without true Alimentary Canal. |
No foot-like appendages. Gymnica. |
Form of body constant. |
Self-division complete. |
illoricated, or without shell ..... | MONADINA. | |
| Self-division incomplete. |
loricated, or shelled ..... | CRYPTOMONADINA. | ||||
| Form of body variable. |
illoricated ..... | self-division ..... | HYDIOMORINA. | |||
| loricated ..... | self-division general and globular | VOLVOCINA. | ||||
| With variable foot-like processes. Pseudopoda. |
illoricated ..... | self-division unilateral |
illoricated ..... | VIBRIONIA. | ||
| (filiform).... | loricated ..... | CLOSTERINA. | ||||
| Hairy. Epitricha. |
illoricated ..... | illoricated ..... | ASTASLEA. | |||
| loricated ..... | DINOERYINA. | |||||
| Foot-like processes, compound ..... | illoricated ..... | illoricated ..... | AMOEBA. | |||
| loricated ..... | ARCCELLINA. | |||||
| Foot-like processes, simple ..... | illoricated ..... | illoricated ..... | BACILLARIA. | |||
| loricated ..... | CYCLIDINA. | |||||
| PERIDINÆA. | ||||||
1 Annals of Natural History, vol. vi. p. 156, 1850. Similar observations had been made by Mr Girard, who states that Kolpoda cucullus is an embryonic stage of a species of Planaria.
2 Hist. des Infusoires, p. 273.
3 Die Infusionsthierchen als vollkommene organismen. Ein Blick in das tiefere Leben der organischen Natur. Atlas mit 64 illumirten Kupfertafeln, gr. fol. Leipzig, 1838.
| Animal-cule. | Family. | Animal-cule. | |
|---|---|---|---|
| ENTERODELA, with an Alimentary Canal. |
One orifice. | { illiciated | VORTICELLINA. |
| Anopisthia. | { loricated | ||
| Two opposite orifices. |
{ illiciated | OPHEYDINA. | |
| { loricated | |||
| Enantiotreta. | { illiciated | ENCELIA. | |
| Orifices situated obliquely. |
{ loricated | ||
| { illiciated | { with proboscis, no tail | COLEPINA. | |
| { loricated | { anterior mouth, a tail | TRACHELINA. | |
| Orifices abdominal. |
{ illiciated | { locomotive cilia | OPHYOCERINA. |
| { loricated | { locomotive organs | ASPIDISCINA. | |
| Catotreta. | { illiciated | { locomotive cilia | KOLPODEA. |
| { loricated | { locomotive organs | OXYTRICHINA. | |
| EUFLOTA. |
We shall conclude by observing that some years ago an idea became prevalent that animalcules might be manufactured by means of galvanism. The results of some of the experiments proved too much, for the creatures when examined were found to belong, not to the Infusorial tribes, but to the Arachnides, a class more highly organized than even Insects.1 That the earlier naturalists, labouring under the disadvantage of imperfect glasses should have made mistakes is not surprising; but we read with wonder, in the year 1833, Dutrochet's statement that all the globular and elliptical Infusoria were merely vesicles set in motion by streams of electricity, and so might be artificially produced. In the following year Cagniard Latour declared that he had manufactured animalcules by means of carburetted hydrogen. But M. Audouin's examination proved that they were Entomostraca, and that the method employed in their production was fallacious. The following is Ehrenberg's account of some curious experiments on these imaginary productions by Professor Bondsdorff, communicated to the German Naturalists' Association in 1834. If a solution of chloride of aluminum be dropped into a solution of potassa, by the attenuate solution of the aluminum in the excess of alkali, an appearance will be given to the drop of aluminated matter, by the chemical changes and reactions which take place, as if the Amaba diffuens were actually present, both as to its form and evolution, and it will seem to be alive. Such appearance, adds Bondsdorff, bears the same relationship to the real animalcule as a doll or figure moved by mechanism does to a living child.
The English reader will consult with advantage Mr Pritchard's History of Infusorial Animalcules, living and fossil; new edition, enlarged, Lond. 1852. A great mass of useful information is there collected, and Ehrenberg's system is given in detail. F. T. Kützing's Die Bieselschaligen Bacillarien od. Diatomeen, 1844, is an excellent work. Dujardin's has been already named in full, as perhaps the best systematic work we have on animalcules at the present time. Mr Ralfs' recent monograph on the British Desmidiae (Lond. 1848) will be found indispensable; as also the Rev. William Smith's Synopsis of the British Diatomaceæ, vol. i. Lond. 1853.
The following is a list of papers published in the Annals of Natural History, from which much useful information will be gained:—On the existence of Infusoria in Plants; by Professor Morren; vol. vi. p. 344. On the Sacculi of Polygastria; by Dr J. W. Griffiths; vol. xi. p. 438. On the production of Infusoria in the Stomachs of Herbivorous and Carnivorous Animals; by MM. Gruby and Delafond; vol.
xiii. p. 154. On Microscopic Life in the Ocean; by Professor Ehrenberg; vol. xiv. p. 169. Abundant Occurrence of rare Infusoria in the Scallop; by H. Lee; vol. xv. p. 371. Microscopical Examination of the Chalk and Flint of the south-east of England; by Dr Mantell; vol. xvi. p. 73. On the Organization of the Polygastric Infusoria; by C. Eckhard; vol. xviii. p. 433. On Conjugation in the Diatomaceæ; by G. H. K. Thwaites; vol. xx. pp. 9 and 343. On the Siliceous Polycystina of Barbadoes; by Professor Ehrenberg; vol. xx. p. 115.
The following papers are from the new series of the Annals:—On the British Lagenæ; by W. C. Williamson; vol. i. p. 1. On the Diatomaceæ; by G. H. K. Thwaites; vol. i. p. 161. On a new British Species of Campylodiscus; by W. C. Williamson; vol. i. p. 321. Notes on Diatomaceæ; by Professor Dickie; vol. i. p. 322. On Fossil Diatomaceæ in Aberdeenshire; by Professor Dickie; vol. ii. p. 93. On a Diaceous Rotifer; by T. Brightwell; vol. ii. p. 153. On the colour of a Fresh-Water Loch; by Professor Dickie; vol. iii. p. 20. On the Mode of Growth in Oscillatorie; by J. Ralfs; vol. iii. p. 39. Observations on Recent Foraminifera; by W. Clark; vol. iii. p. 380. On two new species of Floscularia; by Dr W. M. Dobie; vol. iv. p. 233. On the Development of Trichodina pediculus; by J. T. Arlidge; vol. iv. p. 269. On the Conjugation of Closterium Ehrenbergii; by the Rev. W. Smith; vol. v. p. 1. On Deposits of Diatomaceous Earth on the shores of Lough Morne, county Antrim; by the Rev. W. Smith; vol. v. p. 121. On Nyctotherus, a new genus of Polygastria; by Dr Leidy; vol. v. p. 156. On the Recent Foraminifera; by W. Clark; vol. v. p. 161. On the Nostochineæ; by J. Ralfs; vol. v. p. 321. On Asplanchna priodonta; by P. H. Gosse; vol. vi. p. 18. Notes on the Diatomaceæ, with descriptions of the British species included in the genera Campylodiscus, Surirella, and Cymatopleura; by the Rev. W. Smith; vol. vii. p. 1. On three new species of Animalcules; by J. Alder; vol. vii. p. 426. On the Germination of the Spore in the Conjugateæ; by the Rev. W. Smith; vol. viii. p. 302. On the Cell-Membrane of Diatomaceous Shells; by J. W. Bailey; vol. viii. p. 157. Remarks on Dickiea; by J. Ralfs; vol. vii. p. 204. Catalogue of the Rotifera found in Britain, with descriptions of five new genera, and thirty-two new species; by P. H. Gosse; vol. viii. p. 197. On Chantansia; by J. Ralfs; vol. viii. p. 302. Notes on the Diatomaceæ, with Descriptions of the British Species, included in the genus Pleurosigma; by the Rev. W. Smith; vol. ix. p. 1. (J. W.)
1 For example, the animal obtained by Mr Crosse by means of galvanism was an Acarus. It was afterwards stated to be a well-known species, common in houses, and not unlikely to make its accidental way into a philosophical apparatus.