every class, order, and even genus of animals, except a very few of the soft worms and insects in their first and unfinished state.

It is hence the cerambyx, and several other tribes of insects, are able to make that shrill sound which they give forth on being taken, and which appears like a cry from the mouth, but is in reality nothing more than the friction of the chest of the insect against the upper part of its abdomen and wing-shells. And it is hence, also, that the ptinus fatidicus, or deathwatch, produces those measured strokes against the head or other part of a bed in the middle of the night, which are so alarming to the fearful and superstitious; but which in truth are nothing more than a call or signal by which the one sex is enticed to the other, and is merely produced by the insect's striking the bony or horny front of its head against the bed-post, or some other hard substance,

Having, then, taken a brief survey of the elementary nature and chemical composition of these harder parts of the animal frame, I shall proceed to make a few remarks upon the relative powers of each, and their diversified applications amid the different kinds of animals in which they are employed.

The BONES in their colour are usually white; but this does not hold universally, for those of the gar-pike (esox Belone) are green; and in some varieties of the common fowl they approach to a black: Abelfazel remarks this of the fowls of Bera, and Niebuhr of those of Persepolis.

The bones of an animal, wherever they exist, are unquestionably the levers of its organs of motion: and so far the mechanical theorists are correct. In man and quadrupeds, whose habits require solidity of strength rather than inflexibility of accommodation, they are hard, firm, and unpliant, and consist of gluten fully saturated with phosphate and carbonate of lime. In serpents and fishes, whose habits, on the contrary, demand flexibility of motion, they are supple and cartilaginous; the gluten is in excess, and the phosphate of lime but small in proportion to it, and in some fishes altogether deficient in the composition of their skeleton, though still traceable in their scales and several other parts. In birds, whose natural habits demand levity, the bones are skilfully hollowed out and communicate with the lungs, and instead of being filled with marrow are filled with air, so that the purpose for which the structure of birds was designed is as obvious, and as deeply marked, in the bones as in the wings, whose quills also are for the same reason left hollow, or rather are filled with air, and in many tribes communicate with the lungs as the bones do.

The skeleton of the cuttle-fish (sepia officinalis) is extremely singular; its back-bone, for some purpose unknown to us, is much broader than that of any other aquatic animal of the same size, and of course would be much heavier but for a curious contrivance to prevent this effect, which consists in its being exquisitely porous and cellular, and capable, like the bones of birds, of becoming filled with air, or exhausted of it, at the option of the animal, in order to ascend or descend with the greater facility. It is an animal of this kind, or closely akin to it,* that inhabits the shell of the

*The animal has commonly been supposed to be a real sepia or cuttle-fish; but several naturalists have of late doubted this, inasmuch as there are a few marks of distinction that seem to take it out of this genus. Rafinesque has hence made another genus, for the purpose of receiving those which possess these distinctive signs; and Dr. Leach has lately distinguished it specifically, in consequence of specimens sent home from the unfortunate Congo expedition, as collected by Cranch, by the name of Ocythe Cranchii. Even this animal, however, is regarded as a parasite in the shell, and only possessing it when empty. The proper animal is not known to the present hour. See Phil. Trans. 1817, p. 293.

beautiful paper-nautilus, and still more beautiful pearl-nautilus (argonauta and nautilus tribes,) and which hence obtain no inconsiderable portion of that lightness which enables them, with their extended sails, to scud so dexterously before the wind. In the calamary (sepia Loligo) we meet with an approach towards the same contrivance, in a kind of leafy plate introduced into the body of the animal; and even in the cloak of the slug tribe we trace something of the same sort, though proportionably smaller, and verging to the nature of horn.

Generally speaking, the bones grow cartilaginous towards their extremities, and the muscles tendinous; by which means the fleshy and osseous parts of the organs of motion become assimilated, and fitted for that insertion of the one part into the other upon which their mutual action depends. The extent and nature of the motion is determined by the nature of the articulation, which is varied with the nicest skill to answer the purpose intended. In ostraceous worms the only articulation is that of the hinge: in the cancer tribes the tendon is articulated with the crust, whence the wonderful strength and activity of the claws; and it is articulated in a similar manner with the scaly plates of some species of the tortoise. In insects the part received and the part receiving form each a segment of a spheroid; whence the motion may be either rotatory or lateral, at pleasure. In mammalian animals the lower jaw only has a power of motion; but in birds, serpents, and fishes the upper jaw in a greater or less degree possesses a similar power.

The motion of serpents is produced, according to Sir Everard Home, by their ribs, which for the most part accompany them, not only as organs of respiration, but from the hind extremity to the neck, and are possest of a peculiar power of motion by means of peculiar muscles. "The vertebræ are articulated by ball and socket-joints (the ball being formed upon the lower, and the socket on the upper one), and have therefore much more extensive motion than in other animals." In the draco volans the skeleton of the wings is formed out of ribs which "are superadded for this purpose, and make no part of the organs of respiration; the ribs in these animals appear to work in succession, like the feet of a caterpillar."

The TEETH vary in their form and position almost as much as the bones. Where jaw-bones exist they are usually fixt immoveably in their sockets; but in some ar nals a few of them are left moveable, and in others the whole. The mus maritimus, or African rat, the largest species of this genus which has hitherto been discovered, and seldom less than a fullsized rabbit, has the singular property of separating at pleasure to a considerable distance the two front-teeth of the lower jaw, which are not less than an inch, and a quarter long. That elegant and extraordinary creature the Kangaroo, which, from the increase that has lately taken place in his Majesty's gardens at Kew, we may soon hope to see naturalized in our own country, is possessed of a similar faculty. And the hollow tusks or poisoning fangs of the rattlesnake, and other deadly serpents, are situated in a peculiar bone on each side of the upper jaw, so articulated with the rest, that the animal can either depress or elevate them at his option. In a quiescent state they are recumbent, with their points directed inwards; but whenever the animal is irritated he instantly raises them; and at the moment they inflict a wound, the poison, which lies in the reservoir immediately below, is injected through their tubes by the act of pressure itself.

In the shark and ray genera the whole of the teeth are moveable, and lie imbedded in jaw-cartilages instead of in jaw-bones, and like the fangs of

the poisonous serpents are raised or depressed at pleasure. The teeth of the xiphias Gladius, or sword-fish, are similarly inserted; while his long sword-like snout is armed externally, and on each side, with a taper row of sharp, strong, pointed spines or hooks, which are sometimes called his teeth, and which give rise to his popular name.

The ant-eater and manis swallow their aliment whole : and in many animals the jaws themselves perform the office of teeth, at least with the assistance of the tongue. In birds this is generally the case, sometimes in insects, whose jaws are for this purpose serrated or denticulated at the edge, and frequently in molluscous worms. The jaws of the triton genus act like the blades of a pair of scissors. The snail and slug have only a single jaw, semilunar in its form, and denticulated: but the mouth of the nereis has several bony pieces. The sea-mouse (aphrodita aculeata) has its teeth, which are four, fixed upon its proboscis, and is of course able to extend and retract them at pleasure; and the leech has three pointed cartilaginous teeth, which it is able to employ in the same way, and by means of which it draws blood freely. In like manner, though insects chiefly depend upon a serrated jaw, yet many of them are also possessed of very powerful fangs, of which we have a striking instance in the aranea avicularia, or bird-spider, an inhabitant of South America, found among trees, and a devourer of other insects and even small birds. It is of so enormous a size that its fangs are equal to the talons of a hawk; and its eyes, which are eight in number, arranged as a smaller square in the middle of a larger, are capable of being set in the manner of lenses, and used as microscopes.

In many animals, especially the herbivorous, the tongue itself is armed with a serrated apparatus, the papillæ being pointed and recurvated, and enabling them to tear up the grass with much greater facility. In the catkind the tongue is covered with sharp and strong prickles, which enable the animal to take a strong hold; and similar processes are met with in the bat and the opossum. In the lamprey and myxine families, the tongue itself is covered with teeth. In that grotesque and monstrous bird the toucan, whose bill is nearly as large as its whole body, the tongue is lined with a bundle of feathers, of the use of which, however, we are totally ignorant, though it is probably an organ of taste.

In the crab and lobster tribes the teeth are placed in the stomach, the whole of which is a very singular organ. It is formed on a bony apparatus, and hence does not collapse when empty. The teeth are inserted into it round its lower aperture or pylorus: their surface is extremely hard, and their margin serrated or denticulated, so that nothing can pass through the opening without being perfectly comminuted. The bones and teeth are moved by peculiar muscles. It is a curious fact, that at the time the animal throws off its shell, it also disgorges its bony stomach and secretes a

new one.

The teeth of the cuttle-fish are arranged not very differently, being situated in the centre of the lower part of the body; they are two in number, and horny, and in their figure exactly resemble the bill of a parrot.

The teeth of the echinus genus (sea-hedge-hog) are of a very singular arrangement. A round opening is left in the centre of the shell for the entrance of the food: a bony structure, in which five teeth are inserted, fills up this aperture; and as those parts are moveable by numerous muscles, they form a very complete organ of mastication.

Such is the variety which the hand of nature, sometimes, perhaps, spor

tive, but always skilful, has introduced into the structure and arrangement of the teeth of animals, or the organs that are meant to supply their place. The SKIN AND ITS APPENDAGES offer an equal diversity, and constitute the next subject of our inquiry.

All living bodies, whether animal or vegetable, are furnished with this integument in all of them it is intended as a defence against the injuries to which, by their situation, they are commonly exposed; and in most of them it also answers the purpose of an emunctory organ, and throws off from the body a variety of fluids, which either serve by their odour to distinguish the individual, or are a recrement eliminated from its living materials. This integument accompanies animals and vegetables from their first formation: it involves equally the seed and the egg; and possessing a nature less corruptible than the parts it encloses, often preserves them uninjured for many years, till they can meet with the proper soil or season for their healthy and perfect evolution.

This is a curious subject, and must not be too hastily passed over. After fish-ponds have been frozen to the very bottom, and all the fishes contained in them destroyed; or after they have been completely emptied, and cleared of their mud; eels and other fishes have been again found in them, though no attempt has been made to re-stock the ponds. Whence has proceeded this reproduction? Many of the ancient schools of philosophy, and even some of those of more modern date, refer us to the doctrine of spontaneous generation, and believe that they have here a clear proof of its truth. But this is to account for a difficulty by involving ourselves in one of a much greater magnitude. It is a petitio principii which we stand in no need of, and which we should be careful how we concede. The reproduced fishes have alone arisen from the ova of those which formerly inhabited the fish-pond; and which, from some cause or other, had sunk so deep into the soil, as to be beyond the germinating influence of the warmth and air contained in the supernatant water, communicated to it by the sun and the atmosphere. But the indestructible texture of the integument which enclosed the fecundated ova has preserved them, perhaps for years, from injury and corruption; and they have only waited for that very exposure to light, air, and warmth, which the removal of the superior stratum of mud has produced, to awaken from their dormant state into life, form, and enjoyment; and but for which they would have remained in the same state, dormant but not destroyed, for ten or twelve times as long a period.

So, in the hollows upon our waste lands, when they have been for some time filled with stagnant water, we not unfrequently find eels, minows, and other small species of the carp genus, leeches* and water insects, and wonder how they could get in such a situation. But the mud which has been emptied out of the preceding fish-pond has perhaps been thrown into these very hollows; or the ova of the animals have been carried into the same place by some more recondite cause; and they have been waiting, year after year, for the accidental circumstance which has at length arrived, and given them the full influence of warmth, water, light, and air.

The ova of many kinds are peculiarly light, and almost invisibly minute. They are hence, when the mud, which has been removed from fish-ponds, becomes dry and decomposed into powder, swept by the breeze into the atmosphere, from which they have occasionally descended into the large

* See Wild. p. 120. note.

tanks which are made in India as reservoirs for rain-water and producing their respective kinds in this situation, have appeared, to the astonishment of all beholders, to have fallen from the clouds with the rain itself. Dr. Thomson, in adverting to this curious fact, observes that it is difficult to account for it satisfactorily.* The explanation now offered will, if I mistake not, sufficiently meet the case.

Many insects can only be hatched in a particular animal organ; and it is the office of the integument of the ovum to preserve it in a perfect state till it has an opportunity of reaching its proper nidus. Thus the horsegadfly, or oestrus equi, deposites its eggs on the hairs of this animal, and sticks them to the hair-roots by a viscous matter which it secretes for this purpose. But here they could never be hatched, though they were to remain through the whole life of the horse: their proper nidus is the horse's stomach or intestines, and to this nidus they must be conveyed by some means or other; and in their first situation they must remain and be preserved, free from injury and corruption, till they can obtain such a conveyance. The integument in which they are wrapped up gives them the protection they stand in need of; and the itching which they excite in the horse's skin compels him to lick the itching part with his tongue; and by this simple contrivance the ova of the gadfly are at once conveyed to his mouth, and pass with the food into the very nidus that is designed for them.

It is the same integument that, by its incorruptibility, preserves the caterpillar during the torpitude of its chrysalid state, while suspended by a single thread from the eaves of an incumbent roof; and which thus enables the worm to become transformed into a butterfly. The larve of the gnat, when approaching the same defenceless state, dives boldly into the water, and is protected by the same indestructible sheath from the dangers of an untried element.

In several species the insect remains in its chrysalid state for many years: the locust, in one of its species at least, the cicada septendecim, appears in numbers once only in seventeen years, and the palmer-worm once only in thirty years; cycles not recognised by the meteorologist, but which are well entitled to his attention: and, through the whole range of their duration, it is the integument we are now speaking of that furnishes the animal with a secure protection.

Whence comes it that plants of distant and opposite climates (for every climate has its indigenous plants as well as its indigenous animals,) should so frequently meet together in the same region? that those which naturally belong to the Cape of Good Hope should be found wild in New Holland? and those of Africa on the coast of Norway? and that the Floras of every climate under the heavens should consociate in the stoves and gardens of our own country? it is the imperishable nature of the integument that surrounds their seeds by which this wonder is chiefly ef fected. Some of these seeds are provided with little hooks, and fasten themselves to the skins of animals, and are thus carried about from place to place; others adhere by a native glue to the feathers of water-fowls, and are washed off in distant scas; while a third sort are provided by nature with little downy wings, and hence rise into the atmosphere, and are blown about by the breeze towards every quarter of the compass. Of this last kind is the light seed of the betula alba, or birch-tree; which, in consequence, is occasionally seen germinating on the summit of the loftiest

*Annals of Philos. viii. p. 70.