they enjoy one common life, and form one perfect and consistent being; but it is not impossible to abstract and prune away some parts, without interrupting the life of the being thus mutilated. We know well that a plant can be deprived of its flowers, leaves, and branches; there may remain nothing but a divided root, with a mutilated stem; and even this vestige of a living being will not cease to enjoy life. Nay, frequently many of the detached parts will themselves become new beings, when placed under circumstances favourable to their development. A branch and a leaf are sometimes adequate to form a vegetable similar, in all its parts, to the being whence they were derived. Upon this fact rest the whole theory and practice of slips and layers. The same thing is found with certain animals. A naked polypus, when cut into several pieces, forms so many new and perfect polypi, which continue to live in exactly the same manner as their original stock. Many of the rays of an Asterias, or Sea-star, may be detached without destroying the animal. The heads of slugs may be cut off, and the animals survive, even without any apparent diminution of their vigour. But what seems still more astonishing, some of the vertebrated animals themselves may be similarly mutilated without being instantly deprived of life. Tortoises and Salamanders, which have been decapitated, will still maintain their existence for a considerable time. The Emperor Commodus used to amuse himself with knocking off the heads of Ostriches while running round the Circus at Rome; and we are told by the historians of the times that they still continued their course. This singular power is even perceptible in the newly-born animals of the class Mammalia, which preserve their existence for a very short period, even when similarly injured. Still, however, these are but exceptions to a general law prevailing throughout the Mammalia, the birds, and even among animals less complex and less elevated in the scale of creation. With these we in general find, that the extirpation of any important organ is incompatible with life. Sudden death speedily follows such an operation. They are only capable of supporting the amputation of a limb or appendage; they can only indure a superficial wound or injury. There exists, among all the Vertebrated Animals, a perfect dependence among their primary organs. If one of these be taken away, the remainder of the body ceases to live. If one of them be sick or wounded, the injury affects the other parts. There are five important organs, the integrity of which is absolutely essential to the continued existence of an animal possessing them; these are the heart, the brain, the organs of respiration, the spinal marrow, and the stomach. When these are once associated in a living animal, their co-existence is indispensable; and any serious division or decapitation of a body, provided with these five organs, is speedily mortal.

The parts of a plant are less united and more independent of each other; while the destruction of a part does not lead to the annihilation of the whole, because plants are nearly homogeneous. The portions remaining are provided with the same organs as the entire being. Precisely the same cause enables those lower animals to exist, which are formed but of one simple stomach. They possess no special and circumscribed organs; each of their divided segments partakes of an equal degree of complexity with the whole. But it is evident that a different result ought to be observed among the higher animals, where the functions necessary to their existence are isolated in special and circumscribed organs. With them the existence of the individual rests upon the exact mutual relation of the varied pieces composing the entire body.

In fact, it is a general rule, which prevails throughout the entire Animal Kingdom, that the organs essential to life are concentrated and intimately united in an animal, according to its elevation in the scale of creation, or, in other words, according as its structure is more or less complex. The variety and intricacy of the wheel-work requires a greater concentration of the moving power.

The symmetrical forms observable in all living beings are surprising. In regard to the roots of plants, and the branches of large trees, we observe that a great irregularity generally prevails. But this is owing rather to inequalities of the soil, and to varieties in the intensity of light, than to any natural disposition to irregularity in the plants themselves. The soil is not composed of uniform materials, and the roots always direct their fibres toward those parts which are most easily moved and yield the most abundant nutriment. The leaves and buds, again, are delicately sensible to nice degrees of light. We accordingly observe that the Coniferæ, such as the Pine and Fir, being resinous and ever-green trees, upon which these powers have least influence, present the most regular and symmetrical forms.

The regular arrangement among plants is nowhere found in greater perfection than among the Labiata. We do not here allude to their flowers, which are not so very remarkable in this respect, but to their square stems, their opposite leaves, their branches, and their peduncles. In most of these plants, each leaf, taken separately, is arranged with regularity. But none even of those can compare with the beautiful symmetry observable in the leaves of the Sensitive Plant, the Acacias, and the Firs. In by far the greater number of plants we find the utmost exactness in the distances between the several divisions of the calyx and corolla,-the flower-cup, and the flower itself; in the dimensions of each stamen, of each pistil; in every compartment of the ovarium, and of the fruit. With the exception of certain flowers analogous to those of the Acacias, of the Labiata, of

the Orchidea, and some others, the irregularities which many occasionally present are due to the abortion of certain parts, to their adherence, or to their transmutation into other forms.

Ascending to the Animal Kingdom, and arriving at the Polypi, those lowest of animated beings, we already find the same symmetrical arrangements. Their cilia, their tentacula, or little arms, these appendages of mere animated sacs, are disposed with regularity, around that single orifice, which we dignify by the name of mouth. It is only in those calcareous and arborescent masses which they form and inhabit, and which compose by their aggregation. rocks, islands, and rudimentary continents, that we fail to observe this regular arrangement. We may recognise the same order in the starry rays of the Euryalia, and in the spinous compartments of the Echini, or Sea-urchins. In respect to insects, the symmetry is exquisite. We find the same quality in many Mollusca, but most particularly in their shells, and in the crustaceous envelops of Crabs and Lobsters.

It is, however, in the higher or Vertebrated Animals, that symmetry is brought to its greatest degree. Their bones, their nerves, their organs of sense, their brain, their muscles, their glands, their gills or lungs, are all arranged in lateral pairs, when their number is even; or they are placed in the exact central axis of the body, when their number is odd. We must admit, however, that it is externally we can best trace this correspondence, for the internal organs are not thus arranged. In this respect the contrast is altogether surprising: in vain we seek for symmetry-in the disposition of the intestines, the liver, or the heart.

This physiological arrangement is ably illustrated by the excellent Dr. Paley. "The regularity of the animal structure," he observes, "is rendered remarkable by the three following considerations:-First, the limbs, separately taken, have not this co-relation of parts, but the contrary of it. A knife taken down the chine, cuts the human body into two parts externally equal and alike; you cannot draw a straight line which will not divide a hand, a foot, the leg, the thigh, the cheek, the eye, the ear, into two parts equal and alike. Those parts which are placed upon the middle or partition line of the body, or which traverse that line, as the nose, the tongue, the lips, may be so divided, or, more properly speaking, are double organs; but other parts cannot. This shows that the correspondency which we have been describing does not arise by any necessity in the nature of the subject; for, if necessary, it would be universal; whereas, it is observed only in the system or assemblage: it is not true of the separate parts; that is to say, it is found where it conduces to beauty or utility; it is not found where it would subsist at the expense of both. The two wings of a bird always correspond; the two sides of a feather frequently do not. In centipedes, millepedes, and the whole tribe of insects, no two legs on the same side are alike; yet there is the most exact parity between the legs opposite to one another. The next circumstance to be remarked is, that, whilst the cavities of the body are so configurated as externally to exhibit the most exact correspondency of the opposite sides, the contents of these cavities have no such correspondency. A line drawn down the middle of the breast, divides the thorax into two sides exactly similar; yet these two sides enclose very different contents. The heart lies on the left side, a lobe of the lungs on the right, balancing each other neither in size nor shape. The same thing holds of the abdomen. The liver lies on the right side, without any similar viscus opposed to it on the left. The spleen indeed is situate over against the liver, but agreeing with the liver neither in bulk nor form. There is no equipollency between these. The stomach is a vessel both irregular in its shape and oblique in its position. The foldings and doublings of the intestines do not present a parity of sides. Yet that symmetry which depends upon the co-relation of the sides, is externally preserved throughout the whole trunk; and is the more remarkable in the lower part of it, as the integuments are soft: and the shape, consequently, is not, as the thorax is by its ribs, reduced by natural stays. It is evident, therefore, that the external proportion does not arise from any equality in the shape or pressure of the internal contents. What is it indeed but a correction of inequalities?—an adjustment, by mutual compensation, of anomalous forms into a regular congeries?-the effect, in a word, of artful, and, if we might be permitted so to speak, of studied collocation? Similar also to this, is a third observation; that an internal inequality in the feeding vessels is so managed, as to produce no inequality of parts which were intended to correspond. The right arm answers accurately to the left, both in size and shape; but the arterial branches, which supply the two arms, do not go off from their trunk, in a pair, in the same manner, at the same place, or at the same angle, under which want of similitude it is very difficult to conceive how the same quantity of blood should be pushed through each artery: yet the result is right;-in the two limbs which are nourished by them, we perceive no difference of supply, no effects of excess or deficiency, Concerning the difference of manner, in which the subclavian and carotid arteries, upon the different sides of the body, separate themselves from the aorta, Cheselden seems to have thought, that the advantage which the left gains by going off at an angle much more acute than the right, is made up to the right, by their going off together in one branch. It is very possible that this may be the compensating contrivance and if it be so, how curious-how hydrostatical!"

Many animals form singular and remarkable exceptions to this general law of symmetry. The Mollusca have generally their digestive orifices, as well as the distinctive characters of sex, placed

on one side of the body, and that is usually the right side. Flat fishes swim on one side; both their eyes are placed on that which is turned uppermost, and this again is almost always the right side. Even in those animals which are most beautifully arranged, one side of the entire body surpasses the other in strength, energy, and activity, and this stronger half of the body is almost always the right side. We can observe this circumstance among the Crustacea; we see it in the side-walk of the Crab; and remarkably so in the Pagurus Bernhardus, or Hermit Crab, where the right forceps is larger than the left. We even see it in the larger birds, and the feathers of the right wing are always stronger and of a better quality than those of the left. The same inequality can be traced among the Mammalia, and in none of them more so than in Man, who is, perhaps, less ambidextrous than any other animal. With him the superiority of the right hand over the left is not altogether the effect of habit, but is founded in nature. In walking, it is the right leg and foot that give the greater impulse to the body; in hopping or leaping, every schoolboy, who is not naturally left-handed, uses his right leg in preference to the left. Diseases of the right are more acute than those of the left side. When a person wishes to examine an object most minutely, he looks at it with one eye, and that is almost always the right eye. Whether it be not a consequence of that more general law, that a concentration of vital force in one organ is followed by a diminution of vigour in others adjacent to it, and that the presence of the heart at the left side deprives that entire division of the body of the vigour enjoyed by the right side, we shall not at present venture to determine.

We have now shown that one general plan can be traced throughout the whole of living beings; that analogies, sufficiently precise, may be observed throughout the Animal and Vegetable Kingdoms; and that in every portion of created existence, we find a degree of unity and perfection, a mutual dependence among their parts, and the most exquisite symmetry in their forms. We shall now proceed to trace the analogy perceptible in the essential functions of all these beings. Whether we examine the arrangements for the continuation of the several species, the manner in which that constant ingress and egress of particles, constituting nutrition, is fulfilled, the temperature belonging to each class of beings, or that necessity which compels every one of them to come in immediate contact with pure air, the results are the same for all. It is only the details in the workmanship of the great artificer that vary, but the same divine hand is perceptible throughout the whole. Thus, all living beings require nutriment, but animals alone receive the food into central cavities, and digest it. To all living beings air is equally essential-all absorb it and respire; but the instruments of respiration are infinitely diversified in the several classes of living beings. Man and other Mammalia, birds, and reptiles, breathe through lungs; the fishes, on the contrary, the Crustacea, and the Mollusca, respire through gills or branchiæ. Insects, again, perform this function through trachea, or minute holes, with which their surfaces are perforated; while many worms and polypi appear only to absorb air through the pores of their skin, with which they are everywhere covered. Plants breathe through their leaves; and many of them, deprived even of leaves, only perform this function through the pores of the epidermis which covers their substance.

Again, in respect to the arrangements for continuing the several species, we observe the same general design, while the means are ever various. How different do we see this function in the Mammalia-those viviparous animals, where the young, already active and nearly perfect, immediately commence, from the moment of their separation from the parent, those instincts and actions, which can be terminated only by death; in the numerous class of oviparous, and in the ovo-viviparous animals! Again, how immense the chasm between all these animals just alluded to, and the lower beings which are destitute of any distinctions of sex!-how different is the function performed by the Polypi, without sexes, without germs, producing their kind only by buds or off-sets! --and then, again, another mighty chasm between these and plants, continuing their species by hermaphrodite flowers, or else by flowers of distinct sexes! Nor even here does variety cease to exist, for many are cryptogamous, or apparently destitute of any means for continuing their species, except by certain minute and almost evanescent sporules or reproductive corpuscles.

In all functions we trace this analogy in the end, and diversity in the means; and nowhere in a greater degree than in the functions peculiar to animals. They all appear to feel, yet many possess no other organ of sensation than the skin. In very many we find no brain, and in others not even can a vestige of nerves be traced. It is evident that they all move spontaneously, yet in many we can find no visible marks of muscles or organs of motion. We shall, however, not enlarge much further on this point, but merely allude to the analogy observable among the Vertebrated Animals. The analogy among the functions and organs of these animals is so remarkable, and the attention which has in consequence been paid to them so great, that we are exceedingly apt to form limited and erroneous views of the other parts of the animal world-we expect to find in the lower animals the same parts, the same functions, which are plainly observable in them. Deeply impressed with their structure and functions, we can scarcely bring ourselves to imagine any living being without circulating fluids, a heart, blood, or vessels. So prejudiced are we in favour of the arrange

ments observable in the higher animals, that we can scarcely imagine any sensitive being without nerves, or any creature capable of moving without muscles. Tournefort even admitted plants to have muscles; nay, further, he actually described them. At the present day, there is little pro bability of our falling into a similar error; yet we are all naturally disposed, on observing a great analogy in the functions of all animals, to suppose them to be identical in their structure.

We have said that the analogy among the Vertebrated Animals is very remarkable. They are all possessed of a spinal column, composed of numerous vertebræ. Within this solid column is lodged the spinal marrow, and it carries at one extremity a well-defended bony case or head, which contains the brain. In all these beings we find a heart, red blood, lungs, or gills; in all, the organs of the five senses are seen in greater or less degrees of perfection: we find nerves, muscles, a digestive canal, more or less complicated, a liver and pancreas, with evident arrangements for continuing the species. With the exception perhaps of one species, they all have their mouths disposed horizontally; and when they have limbs, these are always four in number. This similarity prevails throughout their structure and functions. It is true that their surfaces vary remarkably according to their several destinations, while the organs of motion differ greatly as they may be designed for swimming, flying, or walking. The organs of respiration vary according as they are intended to breathe in water or in the air. But these differences in external arrangement do not prevent us from tracing the most exact analogy among them all. If we take all the organs, one by one, and compare them separately in any two vertebrated animals, we shall find the most exact equivalents in the two beings; the analogy will be found perfect in all the essential circumstances; it is only the details which are observed to differ. The fish at first sight appears to have neither neck nor thorax but on inspecting it more attentively, we find it to be possessed of all the series of vertebræ; and that the different pieces of its thorax are concentrated near the cranium, with which they are almost confounded. M. Geoffroy has illustrated this curious organization of the Fishes in a philosophical and truly interesting manner. There is, however, one very remarkable distinction between these aquatic vertebrata and the aerial vertebrata, in the organs of voice, of which the former are completely deprived.

The principles, which must form the bases of a natural system of classification, have been already explained. A knowledge of internal organization, with the laws of the subordination and co-existence of functions, will alone lead us to this result.

Every function presupposes another function. Thus, when we see a being apparently moving voluntarily when irritated by any stimulant, we infer that it feels. We, therefore, conclude that voluntary motion presupposes sensation. Again, Life is temporary in its action: it therefore presupposes the reproduction of individuals with the extinction, and perhaps also the creation, of new species. We also conclude that circulation presupposes respiration; because, wherever we find a heart, we also meet with lungs, just in the same manner as we invariably find nerves wherever we can discover muscles. In fact, Life is but an aggregation of phenomena produced by organs connected and governed by these laws of coexistence.

But in forming a system of classification, the difficulty consists in detecting the law of subordinations existing among the various combinations of these instruments of Life. Reflection upon the final cause or design of the functions will often lead us to detect these laws; but there are innumerable relations which no discernment could detect, without the nicest dissection of the bodies, or the most arduous observation of the habits of the animals when in their native elements. The anatomist in his laboratory, and the "out-of-door" naturalist, who haunts the wilds of nature, must unite their labours before we can form a satisfactory system of classification.

After examining the internal structure of every known animal, it has been found that some of them have vertebræ, and others have none: this is a fundamental fact. Again, on examining further, it is found that all those having vertebræ are also possessed of a spinal marrow and a complicated brain; that they have always four organs of sense, of various degrees of perfection, with horizontal jaws placed in the head; and that they have never more than four limbs, and always red blood. On the contrary, when the Invertebrated animals are examined, they are never found to possess either a brain or spinal marrow; their senses are not so distinctly marked, their blood is white, or not so red, and they all have more than four limbs, or none whatever. Proceeding further, when the Vertebrated animals are more closely examined, some of them are found to continue their species by eggs-they are oviparous; others, on the contrary, produce their young alive -they are viviparous. The latter are found to be alone possessed of mammæ, for suckling their young, and hence they are called Mammalia.

Whenever, therefore, we find an animal with a bony skeleton, we know that it must either belong to the Mammalia, or to one of the three classes of oviparous Vertebrata. If it have feathers and lungs, it is a Bird; if it have lungs and no feathers, it is a Reptile; if it have gills and not lungs, it is a Fish. On looking further into the details of the structure, there are found other varieties, yet ever coexisting with certain essential differences. We are thus enabled to assign precisely the rank of an animal from knowing the smallest part of one of these essential organs; and we can

even discover the most curious relations between these differences in the structure of animals, and their habits or instincts. All the Carnassiers, or beasts of prey, for example, have the digestive canal more simple, shorter, less powerful, and consequently their body more slender: on the contrary, they have the canine teeth, or parts analogous to them, much longer, stronger, better armed, and moved by muscles of great energy. Birds of prey have the nails of their claws more fitted for tearing, the beak strong and hooked. The lion, and all others of the cat genus, are similarly armed with formidable retractile claws, with alternate and sharp teeth, and with a solid jaw-bone, moved by powerful muscles. These fundamental characters are in a manner reflected throughout the whole structure, in such a manner that, upon examining a process or projection in one of the teeth of a Carnivorous quadruped, or the condyle of its jaw-bone, we can describe the remainder of its frame-work, and write the history of its habits. In the same manner, we can form an estimate of the force with which a bird flies, by examining the formation of its sternum or breast-bone, to which the muscles of the wings are attached. Whenever we find those two small bones, called Marsupial, in the pelvis of an animal, we may be certain that its young are produced before their time; that they are received and protected in a ventral pouch or bag. Finally, we know that the Ruminantia, or ruminating animals, all have a cloven hoof; that they all have four stomachs, and no incisive teeth in the upper jaw; and that all which carry antlers or horns on their front, have no canine teeth in the upper jaw. The history of the Animal Kingdom offers many facts analogous to these.

But we must remark, that all the organs of each being have the most perfect agreement among themselves. Never does Nature unite among them characters of an opposite kind; we never find the teeth and jaw-bone of the Carnassier, with the cloven foot of an herbivorous quadruped. The poets, painters, and statuaries of former times, loved to blend these distinctive characters into imaginary and fantastic forms. Deceived by their fertile imaginations, they knew not the laws regulating their coexistence. Sometimes we see enormous wings that no muscle can move; sometimes the heads of many animals of different species, united to a trunk which belongs to one of them, or perhaps to a different animal. Nature disdains to present the discordant characters of the Cerberus, Demon, or Angels of our painters and our poets. One universal harmony characterizes all her works, and every part of her perfect mechanism corresponds to the whole.

These, then, are the principles of our Classification, founded on the comparative importance of the organs, their constancy, and the laws of their subordination.

A STOMACH represents the Animal Kingdom, and a Roor the Vegetable Kingdom. As these can exist isolated from every other part, we must seek for other organs to form the secondary divisions in the two Kingdoms.

With Animals, we must first examine whether they are vertebrated; and in that case, whether they are viviparous or oviparous; this is, whether they have mammæ or not. If they have none, we must next inquire whether they breathe through lungs or gills; and we may further examine whether they are or are not carnivorous, whether they fly, walk, swim, or crawl.

If, on the contrary, the animals under examination be without vertebræ, we examine the general arrangement of their body, their movements, whether they breathe through branchiæ, tracheæ, or simply through the skin; whether they have one or more hearts, or none whatever; whether they have wings, feet, antennæ, or tentacula; whether they have testaceous coverings, shells, or elytra ; or whether they have nerves, nervous cords, swelling into knots, or an imperfect brain; we may investigate their intestines, or their metamorphoses. In this way, we are conducted by degrees from those first great divisions, which overwhelm us by their magnitude, into the more circumscribed groups of genera and species.

THE ANIMAL KINGDOM,

CONTAINING LIVING BEINGS WITH STOMACHS, ENDOWED WITH SENSATION AND VOLUNTARY

Divisions.

MOTION.

Classes.

Animals with a bony skeleton, consisting of a cranium, spinal column, and generally also of 1. MAMMALIA. I. VERTEBRA-limbs; the muscles attached to the skeleton; dis- 2. AVES tinct organs of sight, hearing, smell, and taste, 3. REPTILIA. in the cavities of the face; never more than four 4. PISCES. limbs; sexes separate; blood always red.

TA