and the fibres will be exhibited in a very beautiful manner. The leaf may be slit into two parts, by splitting the stalk; and the skins peeled from the fibres will also make a good object. This operation is best performed in the autumn; the fibres of the leaves are much stronger at that season, and less liable to be broken.—The internal structure of shells may be observed by grinding them down on a stone: and all ores and minerals should be carefully washed and brushed with a small brush, to remove any foreign matter that may adhere to them.

To view the circulation of the blood, we must ob- serve living animals of the most transparent kind.— A small eel is sometimes used for this purpose; in which case it must be cleaned from the slime naturally adhering to it; after which it may be put into a tube filled with water, where it can be viewed in a satis- factory manner. The tail of any other small fish may be viewed in the same manner, or put upon a slip of flat glass, and thus laid before the microscope. By filling the tube with water when an eel is made use of, Microscope, we prevent in a great measure the sliminess of the animal from foiling the glass.

The particles of the blood form a very curious object, and have been carefully viewed by different philosophers; who, nevertheless, differ from one another very much in their accounts of them. The best method of viewing these is to take a small drop of blood when warm, and spread it as thin as possible upon a flat piece of glass. By diluting it a little with warm water, some of the large globules will be separated from the smaller, and many of them subdivided; or a small drop of blood may be put into a capillary glass tube, and then placed before the microscope. Mr Baker advises warm milk as proper to be mixed with the blood; but Mr Huxley, diluted the blood with its own serum: and by this method he could preserve the small particles entire, and view them distinctly; and thus he found that they were not globular, as had been imagined by other anatomists, but flat. Having shaken a piece of the coagulum of the blood in serum till the latter became a little coloured, he spread it with a soft hair pencil on a piece of thin glass, which he placed under the microscope, in such a manner as not be quite horizontal, but rather higher at one end than the other. Thus the serum flows from the higher to the lower part; and, as it flows, some of the particles will be found to swim on their flat sides, and will appear to have a dark spot in the middle; while others will turn over from one side to the other as they roll down the glass. Many cruel experiments have been tried in order to observe the circulation of the blood in living creatures, and an apparatus has been invented for viewing the circulation in the mesentery of a frog; but as this can answer no useful purpose, and will never be put in practice by persons of humanity, we forbear to mention it.

II. Besides the objects for the microscope already mentioned, there are innumerable others, some hardly visible, and others totally invisible, to the naked eye; and which therefore, in a more peculiar sense, are denominated

Microscopic Animals. They are the animalcules or moving bodies in water, in which certain substances have been infused; and of which there are a great many different kinds. These animalcules are sometimes found in water which we would call pure, did not the microscope discover its minute inhabitants; but not equally in all kinds of water, or even in all parts of the same kind of it. The surfaces of infusions are generally covered with a scum which is easily broken, but acquires thickness by standing. In this scum the greatest number of animalcules are usually found. Sometimes it is necessary to dilute the infusions; but this ought always to be done with water, not only distilled, but viewed through a microscope, lest it should also have animalcules in it, and thus prove a source of deception. It is, however, most proper to observe those minute objects after the water is a little evaporated; the attention being less diverted by a few objects than when they appear in great number. One or two of the animalcules may be separated from the rest by placing a small drop of water on the glass near that of the infusion; join them together by making a small connexion between them with a pin; and as soon as you perceive that an animalcule has entered the microscope, clear drop, cut off the connexion again.

Eels in paste are obtained by boiling a little flour and water into the consistence of bookbinders paste; then exposing it to the air in an open vessel, and beating it frequently together to keep the surface from growing mouldy or hard. In a few days it will be found peopled with myriads of little animals visible to the naked eye, which are the eels in question. They may be preserved for a whole year by keeping the paste moistened with water; and while this is done, the motion of the animals will keep the surface from growing mouldy. Mr Baker directs a drop or two of vinegar to be put into the paste now and then. When they are applied to the microscope, the paste must be diluted in a piece of water for them to swim in.

Numberless animalcules are observed by the microscope in infusions of pepper. To make an infusion for this purpose, bruise as much common black pepper as will cover the bottom of an open jar, and lay it thereon about half an inch thick; pour as much soft water into the vessel as will rise about an inch above the pepper. Shake the whole well together; after which they must not be stirred, but be left exposed to the air for a few days; in which time a thin pellicle will be formed on the surface, in which innumerable animals are to be observed by the microscope.

The microscopic animals are so different from those of the larger kinds, that scarce any sort of analogy seems to exist between them; and one would almost be tempted to think that they lived in consequence of laws directly opposite to those which preserve ourselves and other visible animals in existence. They have been systematically arranged by O. F. Muller; though it is by no means probable that all the different classes have yet been discovered. Such as have been observed, however, are by this author divided in the following manner:

I. Such as have no external organs. 1. Monas : Pandiforme. A mere point. 2. Proteus : Mutabilis. Mutable. 3. Volvox : Sphericum. Spherical. 4. Enchelis : Cylindracea. Cylindrical. 5. Vibrio : Elongatum. Long.

* Membranaceous.

6. Cyclidium : Ovalis. Oval. 7. Paramecium : Oblongum. Oblong. 8. Kolpoda : Sinuatum. Sinuous. 9. Goniun : Angulatum. With angles. 10. Bursaria. Hollow like a purse.

II. Those that have external organs. * Naked, or not enclosed in a shell. 1. Cercaria : Caudatum. With a tail. 2. Trichoda : Crinitum. Hairy. 3. Kerona : Corniculatum. With horns. 4. Himantopus : Cirratus. Ciliated. 5. Leucophra : Ciliatum undique. Every part ciliated. 6. Vorticella : Ciliatum apice. The apex ciliated. * Covered with a shell. 7. Brachionus : Ciliatum apice. The apex ciliated. In the treatise on HELMINTHOLOGY under the fifth order of the clas vernes, viz. Infusoria, the genera here enumerated have already been noticed according to an arrangement somewhat different, and a few of the species have been described. For the sake of those who wish to prosecute microscopical inquiries we shall introduce descriptions of a few more, and particularly those whose habitats are known.

I. Monas.

This is by our author defined to be "an invisible (to the naked eye), pellucid, simple, punctiform worm;" but of which, small as it is, there are several species.

The monas termo or gelatinosa, is a small jelly-like point, which can be but imperfectly seen by the single microscope, and not at all by the compound one. In a full light they totally disappear, by reason of their transparency. Some infusions are so full of them that scarce the least empty space can be perceived; the water itself appearing composed of innumerable globular points, in which a motion may be perceived somewhat similar to that which is observed when the sun's rays shine on the water; the whole multitude of animals appearing in commotion like a hive of bees. This animal is very common in ditch-water, and in almost all infusions either of animal or vegetable substances.

Monas atomus or albidus; white monas with a variable point. This appears like a white point, which through a high magnifier appears somewhat egg-shaped. The smaller end is generally marked with a black point, the situation of which is variable; sometimes it appears on the large end, and sometimes there are two black spots in the middle. This species was found in sea water, which had been kept through the whole winter, but was not very fetid. No other kind of animalcule was found in it.

II. The Proteus.

An invisible, very simple, pellucid worm, of a variable form.

The tenax, running out into a fine point. This is a pellucid gelatinous body, stowed with black molecules, and likewise changing its figure, but in a more regular order than the former. It first extends itself in a straight line, the lower part terminating in a bright acute point. It appears to have no intestines; and when the globules are all collected in the upper part, it next draws the pointed end up toward the middle of the body, which assumes a round form. It goes through a number of different shapes, part of which are described under the article Animalcule. It is found in some kinds of river water, and appears confined almost entirely to one place, only bending side-wise.

III. Volvox.

An invisible, very simple, pellucid, spherical worm.

The punctum; of a black colour, with a lucid point. This is a small globe, with one hemisphere opaque and black, the other having a crystalline appearance; and a vehement motion is observed in the black part.

IV. Enchelis.

A simple, invisible, cylindric worm.

The viridis, or green enchelis, has an obtuse tail, the fore part terminating in an acute truncated angle; the intestines are obscure and indistinct. It continually varies its motion, turning from right to left.

The punctifera, having the fore part obtuse, the hinder part pointed. It is opaque, and of a green colour, with a small pellucid spot in the fore-part, in which two black points may be seen; and a kind of double band crosses the middle of the body. The hinder part is pellucid and pointed, with an incision supposed to be the mouth, at the apex of the fore part. It is found in marshes.

The pupula, with the fore part papillary, is found in dunghill water in November and December: it has a rotatory motion on a longitudinal axis, and moves in an oblique direction through the water. Both ends are obtuse; and the hinder part is marked with a transparent circle, or circular aperture.

V. Vibrio.

A very simple, invisible, round, and rather long worm.

The lineola is found in most vegetable infusions in such numbers, that it seems to fill up almost the whole of their substance. It is so small, that with the best magnifiers we can discern little more than an obscure tremulous motion among them. It is more slender than the monas terma.

The serpens, with obtuse windings or flexures, is found in river water, but seldom. It is slender and gelatinous, resembling a serpentine line, with an intestine down the middle.

The spirillum is exceedingly minute, and twisted in a spiral form, which seems to be its natural shape as it never untwists itself, but moves forward in a straight line, vibrating the hind and fore parts. It was found in 1782 in an infusion of the fucus arvensis.

The vermiculus has a milky appearance, with an obtuse apex, and a languid undulatory motion, like that of the common worm. It is found in marshy water in November. November, but seldom. It is thought to be the animal mentioned by Leeuwenhoek as found in the dung of the frog and spawn of the male libellula.

The fagitta, with a fetaceous tail, has a long and flexible body; broadest about the middle, and filled there also with gray molecules; the fore part being drawn out into a thin and transparent neck, and the upper end thick and black. It is found in salt water, and seems to move by contracting and extending its neck.

VI. Cyclidium.

A simple, invisible, flat, pellucid, orbicular or oval worm.

The bulla, or orbicular bright cyclidium. This is found occasionally in an infusion of hay. It is very pellucid and white, but the edges somewhat darker than the rest. It moves slowly, and in a semicircular direction.

The millium is very pellucid, and splendid like crystal; and of an elliptical figure, with a line through the whole length of it. The motion is swift, interrupted, and fluttering.

VII. Paramaecium.

An invisible, membranaceous, flat, and pellucid worm.

The chrysalis is found in salt water, and differs very little from the former, only the ends are more obtuse, and the margins are filled with black globules.

The verutum is found in ditches, and has an oblong, green, and gelatinous body, filled with molecules; the lower part thicker than the other; and both ends obtuse. It propagates by division.

VIII. Kolpoda.

An invisible, pellucid, flat, and crooked worm.

The lamella is very seldom met with. It resembles a long, narrow, and pellucid membrane, with the hind part obtuse, narrower, and curved towards the top. It has a vacillatory and very singular motion; going upon the sharp edge, not on the flat side as is usual with microscopic animals.

The gallinula is found in fetid salt water; and has the apex somewhat bent, the belly oval, convex, and striated.

The rostrum is found, though seldom, in water where the lemma grows; and has a slow and horizontal motion. The fore part is bent into a kind of hook; the hind part obtuse, and quite filled with black molecules.

The triquetra was found in salt water, and appears to consist of two membranes; the upper side flattened, the lower convex, with the apex bent into a kind of shoulder.

The affinis is found on the sea-coast, and has an elliptic mass in the middle, but is not folded like the former. The margin of the fore part is notched from the top to the middle; the lower part swells out, and contracts again into a small point.

The cucullatus is found in an infusion of the fucus arvensis. It is very pellucid and crystalline, with several globules, and has an oblique incision a little below the apex.

The ren, or crella, is found in an infusion of hay, commonly about 13 hours after the infusion is made, and has a quick and vacillatory motion. Its body is yellow, thick, and somewhat opaque; curved a little in the middle, so that it resembles a kidney; and full of molecules. When the water in which it swims is about to fail, it takes an oval form, is compressed, and at last bursts.

IX. Gonium.

An invisible, simple, smooth, and angular worm.

The pulvinatum is found in dunghills; and appears like a little quadrangular membrane, plain on both sides; but with a large magnifier it appears like a bolster formed of three or four cylindric pillows sunk here and there.

The corrugatum is found in various kinds of infusions; and is somewhat of a square shape, very small, and in some positions appears as streaked.

The truncatum is found chiefly in pure water, and then but seldom. It has a languid motion, and is much larger than the foregoing. The fore part is a straight line, with which the sides form obtuse angles, the end of the sides being united by a curved line. The internal molecules are of a dark green, and there are two little bright vehicles in the middle.

X. Burforia.

A very simple, hollow, membranaceous worm.

The truncatella is visible to the naked eye; white, oval, and truncated at the top, where there is a large aperture defending towards the base. Most of them have four or five yellow eggs, at the bottom. They move from left to right, and from right to left; ascending to the surface in a straight line, and sometimes rolling about while they descend.

The bulina is pellucid and crystalline, having splendid globules of different sizes swimming about with it. The under side is convex, the upper hollow, with the fore part forming a kind of lip.

The hirundinella has two small projecting wings, which give it somewhat of the appearance of a bird; and it moves something like a swallow. It is invisible to the naked eye; but by the microscope appears a pellucid hollow membrane.

The duplicilla was found among duckweed, and appears like a crystalline membrane folded up, without any visible interlines except a small congeries of points under one of the folds.

XI. Cercaria.

An invisible transparent worm with a tail.

The gyrinus greatly resembles the spermatic animalcules. It has a white gelatinous body; the fore part somewhat globular; the hind part round, long, and pointed. Sometimes it appears a little compressed on each side. When swimming it keeps its tail in continual vibration like a tadpole.

The gibba is found in the infusions of hay and other vegetables; Microscope vegetables; and is small, opaque, gelatinous, white, and without any visible intestines.

The *inquieta* is found in salt water, and is remarkable for changing the shape of its body; sometimes it appears spherical, sometimes like a long cylinder, and sometimes oval. It is white and gelatinous, the tail filiform and flexible, the upper part vibrating violently. A pellucid globule may be observed at the base, and two very small black points near the top.

The *turbo*, with a tail like a bristle, is found among duckweed. It is of a tawny appearance, partly oval and partly spherical; and seems to be composed of two globular bodies, the lowermost of which is the smallest, and it has two little black points like eyes on the upper part. The tail is sometimes straight, sometimes turned back on the body.

The *poduria* is found in November and December, in marshy places covered with *Lemna*. It is pellucid; and seems to consist of a head, trunk, and tail: the head resembles that of a herring; the trunk is ventricose and full of intestines, of a spiral form and black colour. The tail most commonly appears to be divided into two bristles. The intestines are in a continual motion when the body moves, and by reason of their various shades make it appear very rough. There are likewise some hairs to be perceived. It turns round as upon an axis when it moves.

The *viridic* is found in the spring in ditches of standing water; and in some of its states has a considerable resemblance to the last, but has a much greater power of changing its shape. It is naturally cylindrical, the lower end sharp, and divided into two parts; but sometimes contracts the head and tail so as to assume a spherical figure.

The *setifera* is found in salt water, but seldom. It is small, the body rather opaque, and of a round figure. The upper part is bright, and smaller than the rest: the trunk is more opaque; the tail sharp, and near it a little row of short hairs. It has a slow rotatory motion.

The *hirta* was likewise found in salt water. It is opaque and cylindrical; and when in motion, the body appears to be surrounded with rows of small hairs separated from each other.

The *pleurometer* is found in water which has been kept for several months. It is membranaceous, roundish, and white, with two blackish points in the fore part, the hinder part being furnished with a slender sharp tail. It has orbicular intestines of different sizes in the middle; the larger of them bright. The motion is vacillatory; and in swimming it keeps one edge of the lateral membrane upwards, the other folded down.

The *tribos* is flat, pellucid, triangular, having each angle of the base or fore part bent down into two linear arms, the apex of the triangle prolonged into a tail. It is found in salt water.

**XII. Leucophora.**

An invisible, pellucid, and ciliated worm.

The *mamilla* is of a dark colour, and filled with globular molecules; short hairs are curved inwards; and it occasionally projects and draws in a little white protuberance. It is pretty common in marshy water.

The *viridescens* is a large, pear-shaped, greenish-coloured animalcule, filled with opaque molecules, and covered with short hairs; generally moving in a straight line. It is found in salt water.

The *burata* is found in salt water, and is similar in many respects to the former. It is of a long oval shape, bulging in the middle, and filled with green molecules, everywhere ciliated except at the apex, which is truncated and shaped somewhat like a purse; the hairs are sometimes collected into little fascicles.

The *potthuma* is globular, and covered as it were with a pellucid net; is found in fetid salt water.

The *fignata* is common in salt water in the months of November and December. It is oblong and subdepressed, with a black margin filled with little molecules, but more particularly distinguished by a curved line in the middle somewhat in the shape of the letter S; one end of which is sometimes bent into the form of a small spiral.

**XIII. Trichoda.**

An invisible, pellucid, hairy worm.

The *gyrus* is one of the smallest of this genus, and is found in salt water. It is smooth and free from hairs, except at the fore part, where there are a few.

The *nigra* was found in salt water, and has an opaque body; but when at rest one side appears pellucid. When in violent motion, it seems entirely black.

The *pubes* is found in water where duckweed grows, chiefly in the month of December. It has a bunch above the hind part marked with black spots, depressed towards the top, a little folded, and somewhat convex on the under part. The apex is furnished with hairs, but they are seldom visible till the creature is in the agonies of death, when it extends and moves them vehemently, and attempting as it were to draw in the very last drop of water.

The *patens* is found in salt water; and is of a long cylindrical shape, filled with molecules, the fore part bright and clear, with a long opening near the top which tapers to a point, and is beset with hairs.

The *friate* is found in the month of December in river water. It is a beautiful animalcule, of a fox colour. It is of an oblong shape, the lower end somewhat larger than the other. It has a set of streaks running from one end to the other, and at the abdomen a double row of little eggs lying in a transverse direction.

The *uvula* is found in the infusion of hay and other vegetables. It is six times longer than broad, round, flexuous, of an equal size, the greater part filled with obscure molecules; the fore part rather empty, with an alimentary canal and lucid globules near the middle. The margin of the fore part is covered with short hairs.

The *linter* is found in air infusion of old grass. It is egg-shaped, oblong, with both extremities raised so that the bottom becomes convex, and the upper part depressed like a boat: it is of different shapes at different ages, and sometimes has a rotatory motion.

The *pavillar* is found in salt water; and is long, full of gray molecules; the fore part truncated and hairy, and rather smaller than the other.

The *vermicularis* is found in river water; and is pel- MIC

Microscope lucid in the fore part, with the hind part full of molecules.

The melita is found in salt water, but very rarely. It is oblong, ciliated, with a globular apex, a dilatable neck, and a kind of peristaltic motion perceivable within it.

The perillum is frequently found in marshes. It is cylindrical, pellucid, mucilaginous, and capable of being folded up. It appears double; the interior part full of molecules, with an orbicular mucilaginous appendage, which it can open and shut, and which forms the mouth. The external part is membranaceous, pellucid, dilated, and marked with transverse streaks; and it can protrude or draw in the orbicular membrane at pleasure. Some have four articulations in the tail, others five; and it has two pairs of brittle, one placed at the second joint, the other at the last.

The delphis is found in river water. It is smooth, pellucid, having the fore part dilated into a semicircle, gradually decreasing in breadth towards the tail. The front is hairy, the hairs standing as rays from the semicircular edge: one of the edges is sometimes contracted.

The delphinus is found in hay that has been infused for some months. It is pellucid, smooth, and egg-shaped; the hinder part terminating in a tail about half the length of the body, dilated at the upper end, truncated, and always bent upwards. It moves sometimes on its belly and sometimes on its side.

The rofifera is found in water where duckweed has been kept. It is depressed, capable of changing its shape, yellow, with long ciliated hairs; it has four feet tapering to a point, one of them longer than the rest. Both feet and hairs are within the margin. The shape of the body is generally triangular; the apex formed into an obtuse beak, which the creature sometimes draws in so that it appears quite round.

The charon was found in salt water. It is oval, and resembles a boat as well in its motion as shape; the upper part is hollowed, the under part furrowed and concave; the stern round, with several hairs proceeding from it.

XIV. Kerona.

An invisible worm with horns.

The rofifera is found in river water. It has three rows of horns on the back, which occupy almost the whole of it.

The cypris is found in water covered with lemma. It is somewhat of a pear shape, compressed, with a broad and blunt fore part; the front furnished with hairs, or little vibrating points inserted under the edge, shorter in the hind part, partly extended straight, and partly bent down, having a retrograde motion.

The calceolium is found in the infusion of vegetables. The body is broad and flat, both sides obtuse, filled with black molecules, and there is a black spot near the hinder part, where there are likewise a few short bristles.

The pyxulata is found in salt water. It is oval, convex; one edge of the hinder part sinuated, both ends set with hairs, and some horns on the fore part.