f a similar kind are likewise found in vinegar; and, like those already described, are found to be viviparous. But it is not only in acid matters that such appearances are observed. In some fields of wheat, many grains may be observed, that appear blackish outwardly, as if scorched; but when opened are found to contain a soft white substance, which, attentively considered, appears to be nothing else than a congeries of threads or fibres lying close to each other in a parallel direction, much resembling the urine down of some thistles on cutting open the flower-heads before they begin to blow. This fibrous matter discovers not the least sign of life or motion, unless water is applied; but immediately on wetting, provided the grains of wheat have been newly gathered, the supposed fibres figurate, and appear to be living creatures. Their motions at first are very languid; but gradually become more vigorous, twisting and wriggling themselves somewhat in the manner of the eels in paste, but always slower than they, and with a great deal of less regularity.
If the grains of wheat are grown dry by keeping, and in that condition are cut open, the fibrous matter is very distinguishable; and, on putting water to it, will separate with great readiness, and seem like fine tubes or threads tapering at both ends: but not the least motion will be perceived till they have been in water for several hours, and sometimes they will never move at all. But if the same grains are steeped in water for three or four hours, or buried for some days in the earth, till they are fully saturated with moisture, and then opened with a penknife; on taking out a small portion of the white matter carefully, and spreading it thin upon a slip of glass, the animalcules will be seen bundled together, and extended longitudinally, but without motion: and though, upon the application of water, they will not revive so soon as those taken from fresh grains, whose moisture has never been exhale; yet, after remaining an hour or two in water, they are constantly found alive and vigorous, even though the grains have been kept in a dry condition for several years.—It is necessary, however, to adapt, in some measure, the time of continuing the grains in water or earth, to the age and dryness of them: for if they are not opened before they are too much softened, the animalcules will be dead; and unless the hulks are opened to let those creatures out after they have been steeped, they inevitably perish in them: otherwise, they will continue alive in water for many months; and, should the water dry away, may be revived again by giving them a fresh supply.
3. The Proteus. This animalcule has been dignified by Mr Baker with the name of Proteus, on account of its assuming a great number of different shapes, so as to scarce be known as the same animal in its various transformations; and indeed, unless it be carefully watched while passing from one shape to another, it will often become suddenly invisible, as happened more than once to Mr Baker.
When water, wherein any sort of vegetable has been infused, or animals preserved, has stood quietly for some days, or weeks, in any glass or other vessel, a flinty substance will be collected about the sides: some of which being taken up with the point of a pen-knife, placed on a slip of glass in a drop of water, and looked at through the microscope, will be found to harbour several kinds of little animals that are seldom found swimming about at large; among which the proteus is one. Its shape is better understood from the figure, than from any description that could be given. Its colour, &c., substance and colour seems to resemble that of a snail; and its whole shape seems to bear a considerable resemblance to that of a swan. It swims to and fro with great vivacity: but will now and then stop for a minute or two; during which time its long neck is usually employed as far as it can reach, forwards, and on every side, with a somewhat slow, but equable motion, like that of a snake, frequently extending thrice the length of its body, and seemingly in search of food.
There are no eyes, nor any opening in the head like a mouth, to be discerned: but its actions plainly prove it to be an animal that can see; for though multitudes of different animalcules swim about in the same water, and its own progressive motion is very swift, it never strikes When the Proteus is alarmed, it suddenly draws in its long neck, represented in fig. 5 and 6, transforming itself into the shape represented in fig. 7, when it becomes more opaque, and moves about very slowly, with the large end foremost. When it has continued some time in this posture, it will often, instead of the head and neck it had formerly, put forth a new one, with a kind of wheel-machinery, represented fig. 8, the motions of which draw a current of water to it from a considerable distance. Having often pulled in and thrust out this short head, sometimes with and sometimes without the wheel-work, the creature, as if weary, will remain motionless for a while; then its head and long neck will be very slowly protruded, as in fig. 9, and it soon resumes its former agility. Sometimes it disposes of its neck and head, as represented in fig. 10.
4. The Wheel-Animal, or Vorticella. This wonderful animalcule is found in rain-water that has stood some days in leaden gutters, or in hollows of lead on the tops of houses; or in the slime or sediment left by such water; and perhaps may also be found in other places; but if the water standing in gutters of lead, or the sediment left behind it, has anything of a red colour in it, one may be almost certain of finding them therein. Though it discovers no signs of life except when in the water, yet it is capable of continuing alive for many months after it is taken out of the water, and kept in a state as dry as dust. In this state it is of a globular shape, exceeds not the bigness of a grain of sand, and no signs of life appear; but, being put into water, in the space of half an hour, a languid motion begins, the globule turns itself about, lengthens itself by slow degrees, assumes the form of a lively maggot, and most commonly in a few minutes afterwards puts out its wheels; swimming vigorously through the water, as if in search of food; or else, fixing itself by the tail, works the wheels in such a manner as to bring its food to it.
Fig. 23. and 24. show the wheel-animal in its globular form; fig. 11. and 12. in its maggot state; and figs. 13. 14. 15. 16. 17. 18. 19. 20. 21. and 22. show the different appearances of its wheels, and also its various intermediate changes between the globular and maggot state.
The most remarkable part of this animalcule is its wheel-work. This consists of a couple of semicircular instruments, round the edges of which many little filaments move themselves very briskly, sometimes with a kind of rotation, and sometimes in a trembling or vibrating manner. When in this state, it sometimes unfastens its tail, and swims along with a great deal of swiftness, seemingly in pursuit of its prey. Sometimes the wheels seem to be entire circles, armed with small teeth, like those of the balance-wheel of a watch, appearing projected forwards beyond the head, and extending sideways somewhat wider than its diameter. The teeth or cogs of these wheels seems to stand very regularly at equal distance; but the figure of them varies according to their position, the degree of their protrusion, and perhaps the will of the animal itself. They appear sometimes like minute oblong squares, rising at right angles from the periphery of a circle, like ancient battlements on a round tower; at other times they terminate in sharp points, and altogether resemble a kind of Gothic crown. They are often seen in a kind of curvilinear direction, all bending the same way, and seeming like so many hooks; and now and then the ends of them will be perceived to be clubbed like mallets. This figure, however, as well as the first, they assume but rarely.
As these wheels are everywhere excessively transparent, except about their circular rim or edge, where the cogs are set, it is very difficult to determine by what contrivance they are turned about, or what their real figure is, though they seem exactly to resemble wheels moving round upon an axis. It is also hardly possible to be certain whether those circular bodies in the marks which the teeth are set, are of a flat form, or hollow, or conical; but they seem rather to be of a conical figure. The difficulty of conceiving how an articulation could be contrived so as to cause a real rotation, hath caused many people imagine that there was a deception in this case: But Mr Baker affirms us, that when the wheels are fully protruded, they never fail to show all the visible marks of a regular rotation; and, in some positions, the same cogs or teeth may be traced by the eye during a complete revolution.
All the actions of this creature seem to imply sagacity and quickness of sensation. At the least touch or quickness of motion in the water, they instantly draw in their wheels; and Mr Baker conjectures, that their eyes are lodged somewheres about the wheels; because, while in the maggot state, its motions are slow and blundering; but, after the wheels are protruded, they are performed with great regularity, swiftness, and steadiness.
Notwithstanding the minuteness of this animalcule, the microscope generally discovers others in the same drop of water, compared with which the wheel-animal may be said to be a whale. The transparency of its body, therefore, allows its internal parts to be seen, which cannot be perceived in the minute animalcules, on account of the smallness of their size. a. Is the appearance Fig. 15. of the head; and though it is everywhere transparent, Description a ring or circle, more particularly remarkable for its clearness, is commonly perceived about the middle of its forehead, a little above the mouth. This, Mr Baker thinks, might justly be called the seat of the brain. Many vessels which seem to take their origin from thence are discernible in the head, wherein some transparent fluid appears continually agitated by a kind of fluctuating motion.
The thorax, b, is joined to the head by a very short neck, c, and appears to be about the fifth part of the whole length of the animal. In the middle of the thorax is placed the heart, d, where its systole and diastole is plainly visible. It is seen through the back of the insect, shutting and opening alternately with great regularity and exactness. Its size is proportionable to the creature's bigness; and its shape, during the systole, is nearly circular, being composed seemingly of two semilunar parts, which then approach each other laterally, and form between them a roundish or horsehoe-like figure, whose upper side is flat, and the under one convex. The diastole is performed by a seeming separation, or opening, of these two semilunar parts, whereby the transverse diameter of the heart is very much enlarged. This separation begins exactly in the middle middle of the lower part next the tail; and opens to such a considerable width upwards, that the two parts, when at their utmost dilatation, seem only joined by an arched vessel at their anterior end. The alternate motions of contraction and dilatation are performed with great strength and vigour, in pretty much the same time as the pulsation of the arteries of a man in health. The motions of the heart are communicated to all the internal parts of the thorax; and seem to extend a great deal further; for a strict examination discovers, at the same time, throughout the whole animal, contractions and dilatations going on, that are apparently correspondent thereto. These motions of the heart, however, are sometimes suspended, or imperceptible, for two or three minutes; after which they are renewed, and go on again with the same regularity as before. From the under part of the thorax proceeds a small transparent horn represented at fig. 11. and 12. It is never visible but when the animal turns on its back or side.
The blood or circulating fluid of the wheel-animal is so absolutely colourless, that the current of it through the vessels is indistinguishable by glases. A sort of irregular agitation of some fluid is indeed perceived, which is perhaps a compound motion of currents running different ways, and forming such an appearance, tho' no single current is anywhere distinctly visible.
Immediately below the thorax is another annular division, e, joining upwards to the thorax, and downwards to the abdomen, the entrance whereof it serves occasionally to enlarge or diminish. The abdomen, f, is by much the largest part of the animal, and contains the stomach and intestines. When the insect is full of food, these bowels appear opaque and of a blood-red colour, extending quite through the belly and great part of the tail, and exhibiting a variety of contractions and dilatations. The belly is capable of stretching out greatly in length, or being shortened very much, and widening its diameter. It assumes many shapes, and becomes occasionally a case for all the other parts of the body.
Besides the abovementioned one, there are found in the waters several other species of animals furnished with wheels, some of which appear to have a rotatory, and others a vibratory, motion. Fig. 25 represents a kind found in the ditch at Norwich, where the hair-like insect is produced. They differ from the foregoing only in having very long tails. Fig. 26, 27, and 28, represent a species of wheel-animals, which are also covered with shells. The body of this species consists of three parts, in like manner as the other; only the thorax and abdomen, in this, are not separated by any gut, or intermediate vessel, but are joined immediately together. The heart is plainly perceived, having a regular systole and diastole, at a, as in the former species. These creatures occasionally draw themselves entirely within their shells; and the shell then appears terminated by five short spikes on one side and two on the other.
The young ones of this species are carried in oval faculae, or integuments, fastened externally to the lower part of their shells somewhere about the tail; these faculae are sometimes opaque only at one end, and seemingly empty at the other; sometimes they appear opaque in the middle, with a transparency all round, as in fig. 26. When a young one is about to burst its integuments, the parent assists it greatly, by wagging its tail, and striking the oval bag, so that the young one's head becomes as it were forced into the water, though the tail cannot be so soon disengaged. In this condition the young one sets its wheel a-going, and exerts all its endeavours to free itself from its confinement. When it has got clear, it swims away, wagging its tail as the old one does, and leaving the integument adhering to the shell of the parent. The old one then uses a number of efforts to get rid of this incumbrance, striking against it with her tail, fixing the end of her tail upon it, and then darting her body forward; with several very odd motions not easy to be described. This kind of wheel-animals are great tormentors of the wa-Pulex Ater-flea, Pulex aquaticus arboricola of Swammerdam; of which a figure is given from that author (Plate XXXII.): fig. 2 shows the natural size of the flea; and fig. 1 shows it magnified, with some of the wheel-animals adhering to it. These insects are often found in great numbers in the same water: and when that is the case, it is not uncommon to discover five or six of these crustaceous wheel-animals fastened by their tail to the shell or horns of the flea; causing it, seemingly, a vast deal of uneasiness; nor can they be driven away, or shaken off, by all the efforts the flea can use for that purpose.
5. The Bell-flower Animal, or Plumed Polyte. These Bell-flower-animalcules dwell in colonies together, from ten to fifteen, (rarely falling short of the former number, or exceeding the latter), in a fliny kind of mucilaginous or gelatinous case; which, out of the water, has no determined form, appearing like a little lump of slime; but, when expanded therein, has some resemblance to the figure of a bell with its mouth upwards; and is usually about half an inch long, and a quarter of an inch in diameter. These bells, or colonies, are to be found adhering to the large leaves of duckweed, and other aquatic plants. They may be most easily discovered by letting a quantity of water, with duckweed in it, stand quietly for three or four hours in glass vessels in a window, or other place whence a strong light comes: for then, if any are about the duckweed, they will be found, on careful inspection, extending themselves out of their cases, and making an elegant appearance.
The bell, or case, which these animals inhabit, being very transparent, all the motions of its inhabitants may be discerned through it distinctly. It seems divided internally into several apartments, or rather to contain several smaller faculi, each of which incloes one of these animals. The openings at the tops of these faculi, are but just sufficient to admit the creature's head and a small part of its body to be thrust out beyond them; the rest remaining always in the case. It can, however, occasionally retire into its case altogether; and never fails to do so when alarmed by any sudden motion of the water, or of the vessel which contains it.
Besides the particular and separate motion which each of these creatures is able to exert within its own case the whole colony, and independent of the rest; the whole colony has a power of altering the position of the bell, or even of removing it from one place to another; and hence this bell is sometimes found standing perfectly upright, as in fig. 29, and 33, and sometimes bending the upper part. part downwards, as in fig. 32. As these animalcules seem not to choose to stay together in societies whose number exceeds 15, when the colony happens to increase in number, the bell may be observed to split gradually, beginning from about the middle of the upper or anterior extremity, and proceeding downwards towards the bottom, as in fig. 32, till they at last separate entirely, and become two complete colonies independent of each other, one of which sometimes removes to another part of the vessel.
The arms of each individual of this colony are set round the head, to the number of 4c, having each the figure of an italic f, one of whose hooked ends is fastened to the head; and all together, when expanded, compose a figure shaped somewhat like a horse's shoe, convex on one side next the body, but gradually opening and turning outwards, so as to leave a considerable area within the outer extremities of the arms. When the arms are thus extended, the creature, by giving them a vibrating motion, can produce a current in the water, which brings the animalcules, or whatever other minute bodies are within the sphere of its action, with great velocity to its mouth, situated between the arms; where they are taken in if liked, or driven away by a contrary motion. The food is conveyed immediately from the mouth or opening between the arms, through a narrow neck, into a passage seemingly correspondent to the oesophagus in land animals; down which it passes into the stomach, where it remains for some time, and then is voided upwards, in small round pellets, thro' a gut whose exit is near the neck. The body consists of three divisions; in the uppermost of which are contained all the abovementioned intestines, which are only to be discerned when the creature is full, at which time they become opaque. The other two divisions, which are probably fixed to the bell, seem to be of no other use than to give the creature a power of contraction and extension. The arms are not able to contract like those of the common polype; but, when the animal retires into its case, they are brought together in a close and curious order, so as to be easily drawn in. Though their general appearance when expanded is that of a cup whose base and top are of an horse-shoe form, they sometimes separate into four parts, and range themselves as in fig. 36, so as to resemble four separate plumes of feathers. Tho' their eyes cannot be discovered, yet Mr. Baker thinks they have some perception of the light; for when kept in the dark, they always remain contracted: but on being exposed to the light of the sun or of a candle, they constantly extend their arms, and show evident signs of being pleased.
Fig. 29 represents one complete colony or bell standing erect, with all the animals out of their kingdom, and their arms extended, exhibiting all together a very pretty appearance. a represents two oval bodies, supposed by Mr. Baker to be eggs.
Fig. 30 shows all the creatures withdrawn into their cells, and the end of the bell hanging downwards.
Fig. 33 shows the bell erect, with only one of the animals coming out, in order to show its connection with the bell.
Fig. 34 shows the head and arms of a single polype closing together, and disposing themselves in order to be drawn into the bell.
Fig. 35 shows one complete animal greatly magnified, to show its several parts more distinctly; viz.: a the head, resembling a horse-shoe; b b, the arms seen from one side; c, the narrow neck; d, the oesophagus; e, the stomach; f, the gut or last intestine thro' which the food passes after being digested in the stomach; g, the anus, where the feces are discharged in little pellets; h i, that part of the bell which surrounds the body of the animal, and clothes upon it when it retires down.
Fig. 37, the head and arms seen in front.
6. The Globe-animal. This animalcule, represented fig. 38, seems exactly globular, having no appearance m.a.l. of either head, tail, or fins. It moves in all directions, forwards or backwards, up or down, either 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 slow, at other times very swift; and, when it pleases, it can turn round, as it were upon an axis, very nimbly, without removing out of its place. The whole body is transparent, except where the circular black spots are shown in the figure. Some of the animals have no spots, and others from one to seven. The surface of the whole body appears, in some, as if all over dotted with points; in others, as if granulated like shagreen; but their more general appearance is, as if beset thinly round with short moveable hairs or bristles, which probably are the instruments by which their motions are performed. These animalcules may be seen by the naked eye, but appear only like moving points.
7. The Pipe-animal. These creatures are found on pipe-animals, the coast of Norfolk, living in small tubes or cases of sand, sandy matter, in such multitudes as to compose a mass sometimes of three feet in length. Fig. 39 shows a piece of such a congeries broke off, where a a a represent the mouths or openings of the pipes wherein the little animals make their abode. Fig. 40 shows one single pipe, with its inhabitant, separated from the rest, and magnified nine or ten times in diameter. The pipe or case b is made of sand, intermixed here and there with minute shells, and all cemented together by a glutinous slime, probably issuing from the animal's own body c, which is composed of muscular ringlets like those of a worm, capable of great extension or contraction. The anterior end or head, d, is exceedingly beautiful, having round it a double row of little arms disposed in a very regular order, and probably capable of extension, in order to catch its food, and bring it to its mouth. Some of these tubes are found petrified, sometimes and constitute one species of syringoides.
8. An insect with net-like arms. The properties and shape of this little animal are very extraordinary. It is found only in caledonides, where the water runs very swift, net-like. There these insects are found in clusters, standing erect on their tails; and resembling, when all together, the combs of bees at the time they are filled with their aureliae. On being taken out of the water, they spin threads, by which they hang exactly in the same manner as the garden-spider. Fig. 42 shows one of these insects magnified. Its body appears curiously turned as on a lathe; and at the tail are three sharp spines, on which it raises itself, and stands upright in the water; but the most curious apparatus is about its head, where it is furnished with two instruments like fans or nets, which serve to provide its food. These it frequently spreads out and draws in again; and when drawn up they are... are folded together with the utmost nicety and exactness, so as to be indiscernible when brought close to the body. At the bottom of these fans a couple of claws are fastened to the lower part of the head, which, every time the nets are drawn in, conduct to the mouth of the animal whatever is taken in them. When the creature doth not employ its nets, it thrusts out a pair of sharp horns, as in fig. 41, where the insect is shown magnified about 400 times.
Some of these creatures being kept with water in a vial, most of them died in two days; and the rest, having spun themselves transparent cases (which were fastened either to the sides of the glass, or to pieces of glass put into it), seemed to be changed into a kind of chrysalis: but before taking this form, they appeared as in fig. 43, which shape they likewise assumed when weary with catching their food, or when lying in wait for it. None of them lived above three days; and though fresh water was given them two or three times a day, yet in a few hours it would think to a degree scarce conceivable, and that too at several yards distance, though, in proportion to the water, all the included insects were not more than as 1 to 1,500,000. This makes it probable, that it is necessary for them to live in a rapid stream, lest they should be poisoned by the effluvia issuing from their own bodies, as no doubt they were in the vial.
9. A curious aquatic worm. This animalcule is shown, magnified, at fig. 31. It is found in ditch-water; and is of various sizes, from \( \frac{3}{4} \) to \( \frac{1}{4} \) an inch in length. About the head it has somewhat of a yellowish colour; but all the rest of the body is perfectly colourless and transparent, except the intestines, which are considerably opaque, and disposed as in the figure. Along its sides are several papillae, with long hairs growing from them: it has two black eyes, and is very nimble. But the most remarkable thing in this creature is a long horn or proboscis; which, in the large ones, may be seen with the naked eye, if the water is clear, and is sometimes \( \frac{1}{2} \) of an inch in length: this it waves to and fro as it moves in the water, or creeps up the side of the glass; but it is not known whether it is hollow, or of what use it is to the creature itself.
10. Spermatic Animals, and Animalcula Infusoria. The discovery of living animalcules in the semen of most animals is claimed by Mr. Lewenhoeck and Mr. Nicholas Hartsoeker; who both say they published it about the end of the year 1677 or beginning of 1678: but Mr. Lewenhoeck having given the most particular description of, and made by far the greatest number of experiments concerning them, the discovery is commonly attributed to him.
According to this naturalist, these animalcules are found in the semen mafculinum of every kind of animal; but their general appearance is very much the same, nor doth their size differ in proportion to the bulk of the animal to which they belong. The bodies of all of them seem to be of an oblong oval form, with long tapering slender tails issuing from them; and as by this shape they resemble tadpoles, they have been frequently called by that name; tho' the tails of them, in proportion to their bodies, are much longer than the tails of tadpoles are: and it is observable, that the animalcules in the semen of fishes have tails much longer and more slender than the tails of those in other animals; in somuch, that the extremity of them is not to be discerned without the best glasses, and the utmost attention. Fig. 21. N° 1, 2, 3, 4, represent the spermatic animalcule of the rabbit; and N° 5, 6, 7, 8, those of a dog; according to Mr. Lewenhoeck.
The numbers of these animalcules are inconceivable. Inconceivably numerous, with a microscope the millet or semen mafculinum of a living cod-fish, innumerable multitudes of animalcules were found therein, of such a diminutive size, that he supposed at least 10,000 of them capable of being contained in the bulk of a grain of sand; whence he concludes, that the millet of this single fish contained more living animalcules than there are to be found people living in the whole world. To find the comparative size of these animalcules, Mr. Lewenhoeck placed an hair of his head near them; which hair, thro' his microscope, appeared an inch in breadth; and he was satisfied, that at least 60 such animalcules could easily lie within that diameter; whence, their bodies being spherical, it follows, that 216,000 of them are but equal to a globe whose diameter is the breadth of a hair. He observed, that when the water wherewith he had diluted the semen of a cod-fish was exhaled, the little bodies of the animalcules burst in pieces; which did not happen to those in the semen of a ram: and this he imputes to the greater firmness and consistency of the latter, as the flesh of a land-animal is more compact than fish.
These animalcules appear to be very vigorous, and are continuous of life; for they may be observed to move mutually in long after the animal from which they are taken is dead. They have this peculiarity also, that they are continually in motion, without the least rest or intermission, provided there is fluid sufficient for them to swim about in. These animalcules are peculiar to the semen; nothing that has the least token of life being discovered, by the best glasses, either in the blood, spittle, urine, gall, or chyle. Great numbers, however, are to be found in the whitish matter that sticks between the teeth; some of which are of an oval figure, and others resemble eels.
The Animalcula Infusoria, take their name from their Animalcula being found in all kinds either of vegetable or animal Infusoria, infusions. Indeed, there is scarce any kind of water, unless impregnated with some mineral substance, but what will discover living creatures.—Mr. Lewenhoeck says, that at first he could discern no living creatures in rain-water; but after standing some days, he discovered innumerable animalcules, many thousands of times nimbler than a grain of sand, and in proportion to a mite in rain-water as a bee is to a horse.—In other rain-water, which had likewise stood some time, he found the smallest form he had ever seen; and, in a few days more, met with others eight times as big as these, and almost round.—In another quantity of rain-water, that had been exposed like the former, he discovered a kind of animalcules with two little horns in continual motion. The space between the horns was flat, though the body was roundish, but tapering a little towards the end; where a tail appeared, four times as long as the body, and the thickness of a spider's web. He observed several hundreds of these within the space a grain of sand would occupy. If they happened on the least filament or string, they were entangled in it; and then would extend their bodies into an oblong round, and struggle hard to disengage their tails. He observed a second fort. sort of an oval figure, and imagined the head to stand at the sharpest end. The body was flat, with several small feet moving exceeding quick, but not discernible without a great deal of attention. Sometimes they changed their shape into a perfect round, especially when the water began to dry away. He met also with a third fort, twice as long as broad, and eight times smaller than the first; yet in these he discerned little feet, whereby they moved very nimbly. He perceived likewise a fourth fort, a thousand times smaller than a loupe's eye, and which exceeded all the rest in briskness: he found these turning themselves round, as it were upon a point, with the celerity of a top. And he says, there were several other forts.
The production of animalcula infusoria is very surprising. In four hours time, an infusion of cantharides has produced animalcula less than even the tails of the spermatic animals we have already described. Neither do they seem to be subject to the fate of other animals; but, several kinds of them at least, by dividing themselves in two, to enjoy a fort of immortality. Nor do the common methods by which other animals are destroyed, seem to be effectual for destroying their vital principle. Hot mutton-gravy, secured in a phial with a cork, and afterwards set among hot ashes to destroy as effectually as possible every living creature that could be supposed to exist in it, has nevertheless been found swarming with animalcules after standing a few days.
On the 25th of May 1768, Fahrenheit's thermometer 70°, I boiled a potato in the New-River water till it was reduced to a mealy consistence. I put part of it, with an equal proportion of the boiling liquor, into a cylindrical glass-vessel that held something less than half a wine-pint, and covered it close immediately with a glass-cover. At the same time, I sliced an unboiled potato; and, as near as I could judge, put the same quantity into a glass-vessel of the same kind; with the same proportion of New River water not boiled; and covered it with a glass cover; and placed both vessels close to each other.
On the 26th of May, 24 hours afterwards, I examined a small drop of each, by the first magnifier of Wilson's microscope, whose focal distance is reckoned at 3/8th part of an inch; and, to my amazement, they were both full of animalcula of a linear shape, very distinguishable, moving to and fro with great celerity; so that there appeared to be more particles of animal than vegetable life in each drop.
This experiment I have repeatedly tried, and always found it to succeed in proportion to the heat of the circumambient air; so that even in winter, if the liquors are kept properly warm, at least in two or three days the experiment will succeed.
What I have observed are infinitely smaller than spermatic animals, and of a very different shape: the truth of which every accurate observer will soon be convinced of, whose curiosity may lead him to compare them; and I am persuaded he will find they are no way akin.
At present I shall pass over many other curious observations, which I have made on two years experience, in order to proceed to the explaining a hint which I received last January from Mr De Saussure of Geneva, when he was here; which is, that he found one kind of these animalcule infusoria that increase by dividing across into nearly two equal parts.
I had often seen this appearance in various species a year or two ago, as I found upon looking over the minutes I had taken when I made any new observation; but always supposed the animal, when in this state, to be in coition.
Not hearing, till after M. De Saussure left this kingdom, from what infusion he had made his observation; his friend Dr de la Roche of Geneva informed me, the latter end of February last, that it was from hempseed.
I immediately procured hempseed from different feedsmen in distant parts of the town. Some of it I put into New-River water, some into distilled water, and some I put into very hard pump-water. The result was, that in proportion to the heat of the weather, or the warmth in which they were kept, there was an appearance of millions of minute animalcule in all the infusions; and, sometime after, some oval ones made their appearance, as at fig. 3. b. c. These were much larger than the first, which still continued; these wriggled to and fro in an undulatory motion, turning themselves round very quick all the time that they moved forwards.
I was very attentive to see these animals divide themselves; and at last I perceived a few of the appearance of fig. 3. a., as it is represented by the first magnifier of Wilson's microscope; but I am so well convinced by experience that they would separate, that I did not wait to see the operation; however, as the following sketches, which I have drawn from five other species, will very fully explain this extraordinary phenomenon, there will be no difficulty in conceiving the manner of the first. See figs. 4, 5, 6, 7, 8.
The proportion of the number of these animals which I have observed to divide in this manner, to the rest, is scarce 1 to 50; so that it appears rather to arise from hurts received by some few animalcule among the many, than to be the natural manner in which these kinds of animals multiply; especially if we consider the infinite quantity of young ones which are visible to us through the transparent skins of their bodies, and even the young ones that are visible in those young ones while in the body of the old ones.
But nothing more plainly shows them to be zoophytes than this circumstance, That when, by accident, the extremity of their bodies has been shrivelled for want of a supply of fresh water, the applying more fresh water has given motion to the part of the animal that was still alive; by which means, this shapeless figure has continued to live and swim to and fro all the time it was supplied with fresh water.
I cannot finish this part of my remarks on these animals, without observing, that the excellent Linnæus has joined the berœi with the volvox, one of the animalcule infusoria. The berœi is a marine animal, found Berœi de our coasts; of a gelatinous transparent nature, and scribed of an oval or spherical form, about half an inch to an inch diameter; divided like a melon into longitudinal ribs, each of which is furnished with rows of minute fins; by means of which, this animal, like the animalcule infusoria, can swim in all directions with great swiftness.