Abridgment of the Contemplation of Nature By Mr. Bonnet, of GENEVA

 

  1. From the immutability of species amidst the perpetual motion that reigns in the universe, is deduced the indivisibility of the first principles of bodies: and the indivisibility of these principles would demonstrate the simplicity of their nature, if God had not power to render the highly compounded particles incapable of separation.

The nature of elementary atoms, their forms, relative proportions, and the manner whereby they effect the formation of bodies, are branches of knowledge that surpass the reach of the human mind.

So that we cannot determine whether there are as many species of elements as of bodies; or whether the same elementary particles, variously combined, give birth to different compounded species .*

We are likewise ignorant what it is that essentially distinguishes one body from every other; those we call essential characters are only the ultimate result of the first principles.

0 how interesting would the sight be, were we permitted to penetrate into these principles! A new world would disclose itself to our view; nature then become transparent, would no longer conceal her way from us her laboratories and workshops would then be thrown open. Here we should see her collecting the principles of metals there behold her preparing the colour of the rose. Farther, we-might trace her footsteps into the wonders of light and electricity in other places should observe her sketching the outlines of a plant or animal. Astonished at the sight of this admirable work, we should never be weary of contemplating the infinite diversity of preparations, combinations, and motions, by which it is insensibly brought to its perfection.

*If the elements which constitute the different species of beings, are not simply specific, they must then necessarily be resolved into proportion, which is the same thing; for those proportions will become specific or elementary ratios.

Ye celestial spirits who assisted at the creation of our world, you enjoy these pleasures! Being more favoured than us by time Master of nature, you penetrate into what escapes our notice, and see with’:

what difficulty we creep from one truth to another, as we observe the efforts of an ape to imitate a man.

2. Observe three principal kinds ‘of compositions in terrestrial bodies. 1. That of fluids. 2. That of rude or unorganized solids.

3. That of organized solids.

The first genus, which is the most simple, seems to consist in a bare contact of homogeneous particles, which tend to-wards each other; but the least force divides them.

The second, which is more compounded, is formed of the union of different particles into a solid mass.

The third, still more compounded, is formed of the intermixture of an infinite number of parts, some fluid, and others solid.

3. The small resistance which fluids make to the force that divides-them, their inclination to’ a level, the quickness and ease wherewith they move, penetrate, and separate solids, serve to indicate that they are of all bodies the most simple, subtle, and active.

Fires seems to be a fluid which unites these qualities in the most eminent degree. It is evident from a number of experiments, and particularly from those made by electricity, that fire is a fluid diffused into all bodies, in various proportions. Sometimes it barely fills their pores; at others, is intimately united to their constituent parts, and composes inflammatory matter.

Air and water are likewise contained in the composition of a prodigious number of matters of different kinds. Sometimes they seem to change their nature, and to undergo various transformations ; but these transformations are only imaginary. They resume their primitive state, as soon as the causes which obscured them cease to act.

4. Pure earth is the base or foundation in the’ composition of solids. The chemist meets with it in every body he analyzes. Being fixed and unalterable, it will resist the most violent fire; and’ this immutability of elementary earth, by convincing us of the simplicity of its nature, shows likewise that it is the first step of the scale of inactive solids.

  *Caloric

              From a mixture of pure earth with oils, sulphurs, salts, &c. proceed the various species of more or less compounded earths, which are the proper nourishment of one part of organized bodies.

Bitumens and sulphurs, which are chiefly formed of inflammable matter and earth, seem to lead us from pure earth to metallic substances, in which we discover the same essential principles, only differently combined.

The inalterability of gold from the’ most violent tire, its malleability, and prodigious ductility; equally prove time homogeneousness, extreme fineness, and strict union of it parts.

Other metals are ranged after gold, according to the order of their composition or the stronger or weaker combination of their principles. Platina immediately follows gold: and silver also resists the action of fire ; but is less malleable and ductile than gold, and dissoluble by a much greater number of dissolvents.

Copper appears after silver, and has a great affinity to that metal. It is itself succeeded by tin, lead, and iron.

Those compounds which differ from metals, only by their not being malleable, bear a great resemblance to them, and are called demimetals. Such are antimony, bismuth, spelter.

Vitriols, produced by the union of metallic particles with a coagulated acid, seem to be the passage from metallic substances to salts.

Salts, which always affect determinate and constant figures, indicate thereby the invariableness and simplicity of their principles, whose fundamentals are water and earth.

When they are dissolved by water, or volatilized by air, they become one of the principle causes of the growth of vegetables as they are of fermentations, whose effects are so various and extensive.

The regularity and uniformity of the different kinds of crystallization, sufficiently prove that they are to be attributed to salts, which being dissolved and conveyed by a liquid, and united to foreign matters, compose these pyramidal masses.

Stones, whose species are so numerous, present us with masses of every form, colour, size, and consistence, according to the diversity of liquids, earth, sulphur, metallic parts, salts, places, and other circumstances, which contributed to their formation.

Some of them are perfectly transparent; and these seem to be the most simple. Others are more or less opaque, as their principles are more or less heterogeneous, or more or less mixed.

5. The apparent organization of leafed stones, or such as are divided into layers., as slates, that of fibrous stones, or those composed of filaments, as the amianthus, seem to constitute the passage from rough to organized solids.

We must however allow, that this transition is not so happily’ effected, as those we observe in divers other classes of terrestrial beings.

Organized solids are divided into two general classes: vegetable and animal.

It is not easy to determine precisely the distinction between these two classes. We cannot clearly discern where the vegetable terminates, or the animal commences.

Neither the greater or less degree of simplicity in organization, nor the method of production, nourishing, increasing and multiplying, nor the locomotive faculty, sufficiently enables us to distinguish between these two orders of beings.

There are some animals whose structure appears as simple as that of plants.

What the seed and germ are to the plant, the egg and embryo are to the animal.

The plant and animal increase in equal proportion by an insensible expansion occasioned by nutrition.

The matter received in both of them by inward susception, is there subject to analogous preparations. One part serves as a clothing to the essence of the plant or animal; the rest is evacuated.

There is in plants as well as animals a distinction of sexes; and this distinction in them is followed by the same essential effects that accompany the latter. Several kinds of animals multiply by slips and sprigs; and there are some, that like plants, pass their whole Jives without changing their situation.

If there is any one character, peculiar to the animal, it is that of being furnished with nerves.

6. The plant which seems to occupy the lowest place in the scale of vegetables, is a small unformed mass in which the eye can only perceive a kind of marbling, without any distinct part. This plant is the truffle, the seeds of which are discovered by the microscope.

At a small distance from these, is the numerous family of mushrooms and agarics, which would be taken for different kinds of excres tences, were it not that the eye, by the assistance of a glass, can discover flower and seeds in their folds or cavities.

Liverworts, equal in the number of their species to mushrooms, nearly resemble them. They cleave to the surface of stones, dry wood, trees, &c. sometimes like brown spots, at others in pieces of a circular form, of a gray, or yellow colour, composed of small shells or knobs, or notched like fringe, lace, &c. The seeds are contained in small capsules, invisible to the naked eye, as are likewise the flowers.

  Mosses seem to be species between the mushrooms and liverworts They delight in shade and moisture, and cling to various sorts of bodies. The filaments which issue from them are often of a cotton like nature, and bear flower and seeds.

7. Plants are of three very distinct sorts.

The first, which are for the most part of a small size, delicate constitution, inactive, and abounding in humours, live but a short time; a year is commonly the term of their life.

The second, which are for the most part of a gigantic size, robust constitution, hard, and not so full of humours, live many years, and even for several ages.

The third bear a mean proportion between the first and second.

Herbs are the first, trees the second, and shrubs the third.

These three kinds which are spread over the face of the earth, live promiscuously therein: but there exists in the different classes, an almost infinite diversity of sizes, forms, colours, and inclinations.

They all in common pass their lives in a state of immoveableness. Fixed to the earth by various sorts of fibres, they derive their principal nourishment from it; and with them to live is to expand them selves.

8. The roots, stalk, branches, leaves, flowers, and fruits, comprise all that is most remarkable in the external parts of plants.

The roots, by means of their different kinds of hinges. tuberosities, and ramifications, keep the plant fixed to the earth, while their pores imbibe an exceeding fine slime, which the water liquefies, and carries with it.

From the root springs the stalk, to which the plant partly owes its strength and beauty. Being sometimes shaped like a pipe, it is fortified with knots skilfully disposed. As it is sometimes too weak to support itself, it contrives means to twist itself about a solid prop, or to fasten to it by means of the little hands it is furnished with. Otherwise it appears a strong pillar, bears its proud head aloft in the air, and braves the efforts of storms and tempests.

The branches shoot forth, like so many arms, from the trunk and stalk, on which they are distributed with great regularity. They are divided anti subdivided into many small boughs, and the subdivisions observe the same order as the principal divisions.

The leaves, that charming ornament of plants, are disposed round the stalk and branches with the same symmetry. Some are simple, others compounded, or formed of various foliage. One sort is plain; another indented. Some of them are very thin, others hard, soft, plump, smooth, rough, or hairy.

The flowers, whose enamel is one of the principal beauties of nature, are not less diversified- than the leaves. Some have only a single leaf others several. Here it appears like a large vessel opening itself gracefully; there it forms a grotesque figure in imitation of a muzzle, headpiece, or cowl. Farther still, it is a butterfly, a star, a crown, a radiant sun. Some are dispersed on the plant without any art; others compose nosegays, globes, tufts of feathers, garlands, pyramids.

The greater part of them are furnished with one or more cups, sometimes simple amid plain, at others consisting of several pieces from the centre of the flower proceeds one or several little pillars, either smooth or channeled, rounded at top, or terminating in a point, called pistils, which commonly encompass other smaller pillars, called stamina. These carry on the upper part of them, a sort of small bladders full of exceeding fine powder, every grain of which, viewed through a microscope, appears of a very regular figure, but varied, according to its species. In some they are small, smooth, globes; in others, they are thick set with prickles like the covering of a chesnut, and sometimes they resemble small prisms, or some other regular body.

But how shall we express their fineness, the lively appearance, delicacy, and variety of shadowings, which accompany, in many species of flowers, the sweetness and agreeableness of the perfume

The flowers are succeeded by the fruits and seeds. Magnificent decoration! precious riches, which repair the losses occasioned to plants by the interperateness of seasons, and the necessities of men and other animals.

All fruits and seeds have this in common, they enclose under one of snore coverings the germ of the future plants. Some have only such coverings as immediately enfold the germ, whose outside is of the strongest contexture; and among these, there are some that are provided with wings, tufts, or plumes of feathers, by means of which they are conveyed in the aim or water, by which they are transported and sown in different parts. Others are better clothed, being lodged in sheaths or pods, enclosed in a kind of box, having one or more partitions. A third sort, under a most delicious fruit, which is rendered still more agreeable by its beautiful colour, contain a stone or kernel. Others are enclosed in shells which are either armed with prickles, abound with a bitterjuice, or adorned with fine hair.

The outsides of fruits and seeds do not afford less variety than the leaves and flowers; there is hardly any figure whatever, which they do not furnish a representation of.

9. The inside of plants is composed of four orders of vessels, viz. the ligneous fibres, utriculi, or little bags, the proper vases, and the trachea, or air-vessels.

The ligneous fibres are very small channels deposited according to the length of the plant, and consist of little pipes placed near each other. Sometimes these vessels are parallel, and at others are separated, leaving between them intervals or oblong spaces.

These spaces are filled by the utriculi, a kind of membranous bladders, horizontally disposed, and which communicate with each other.

The proper vases are a kind of ligneous fibres which principally differ from the rest by their juice, which is of a deeper colour or thicker.

In the middle of them, or round a great number of ligneous fibres, are some vessels which are not so narrow, composed of a silvery elastic blade, formed spirewise, like a spring; these are arteries. They seldom contain any thing but air.

These four orders of vessels, which are dispersed through all the parts of the vegetable, in proportion to the functions of each, compose. at least in trees and shrubs, three principal beds : the bark, the wood and the pith.

The bark, or rind, which is the outer covering of plants, and is smooth, even and shining in some, and rough channeled, and hairy in others, is formed of the widest fibres that are the least pressed together, and which admit within them the most air.

The wood, which is placed under the rind, has narrower and more contracted pipes, its utricles less replenished or dilated; and this only has arteries.

The pith, which is situated at the heart of the plant, is little more than a collection of utricles, which are greater and more capacious than those of the bark and wood. They diminish and dry up, as the plant advances in age.

The simplicity of the organization of vegetables is the principal source, of their different methods of multiplication.

A plant pushes out buds from all points of its surface, these buds themselves are plants : being cut and laid in the ground, they take root there, and become entire plants, like that of which they were before only a part.

The smallest branch or leaf may give birth to such a whole plant. Suckers taken from the different plants, and ingrafted in the stalk or branches of another plant, incorporate themselves with it, and being united thereto, form one organical body.

10.  The timorous sensitive plant flies the hand that approaches her: she closes herself again with the utmost speed; and this motion bearing so great a resemblance to that of animals, seems to constitute one of those connexions whereby the vegetable and animal kingdoms, are united.

A little above the sensitive, in a kind of calix, at the bottom of the water, is a small body, exactly resembling a flower. It draws back and entirely disappears when I offer to touch it. It comes out of the calix, and opens itself on my retiring to a distance from it.

  While I was endeavouring in vain to account for this, I discovered by the side of it another body of the same form, but larger, and not lodged in an inclosure. It was supported by a small stalk, whose lower extremity joined to a plant, whilst the other, inclining towards the ground, was divided into several little branches.

I immediately believed it to be a parasite plant; and in order to be more fully convinced of it, I cut it in half between its two extremities.

It soon sprouted out again, and appeared the same as before. I stood awhile to consider it. I saw the little branches move, and extend themselves to several inches in length. They are extremely fine, and spread themselves on all sides.

A little worm came and touched one of these branches: it presently twisted itself about the worm, and by contracting itself, brought it to the upper extremity of the stalk. There I perceived a small aperture, which enlarged itself in order to receive the worm. It was received into a long cavity that encloses the stalk: being there dissolved and digested before my eyes I afterward saw the remainder go out again at the same opening.

The next moment, this singular production separated itself from the plant, and began to walk. The branches after having performed the office of arms, are likewise employed by it instead of legs.

After having made these observations, I could not help acknowledging, that what I took for a parasite plant, was a real animal. I then took a view of the piece I had cut off from it, and perceived, to my surprise, that it had grown, and was become a complete one like the other.

But my surprise was greatly increased, when at the end of some weeks I found these animals were transformed into two very small bushy trees.

From the trunk, which I knew to be the body of the animal, sprung several branches on all sides of it; from these branches smaller ones sprouted forth; and from those, smaller still. They all move different ways, and stretch out their branches, while the trunk continues fixed to a prop. This surprising assemblage form only one entire body; and the nourishment it receives by one of its parts, is successively communicated to all the rest. In short, this collection of bodies divides itself each piece separates itself from the others, and lives distinctly from them.

Amazed at these wonders, I part one of these animals lengthwise, about the middle of the body, I am presently in possession of a monster with two heads.

I repeat the operation a great many times on the same subject, and by this means I gave birth to a hydra, more astonishing than that of Lerna.  

I part several of these animals transversely, and lay the separated pieces end to end. They graft or unite themselves to each other, and compose only one entire animal.

To this prodigy I find a new one succeed. I turn one of these insects, as we do a glove, putting the outside within and vice versa. He does not suffer the least alteration from that: he lives, grows, and multiplies.

These animals which multiply by slips and shoots that we engraft and turn inside out, are polypuses.

They are of a very different species. Many of them never shift their places. Some divide themselves lengthwise, and thus make very pretty nosegays, whose flowers are in clusters.

11. There is a wonderful variety in the construction of animal machines. There are some whose number of parts is very small; others, on the contrary, are very much compounded. In some there are only two or three pieces alike ; others exhibit to us a much greater number. In short, the same parts are differently disposed or combined in different machines.

The perfection of the machines in nature consists, as in those of art, in the number of parts, and diversity of effects. That is accounted the most perfect, which, with the smallest number of parts, produces the greatest variety of effects.

But there is, with respect to ourselves, a considerable difference between the natural and artificial machines : for whereas we may judge of these by an exact comparison of their strength and produce, we can only form our opinion of the others by their consequences.

After this manner we are enabled to judge of the perfection of the human body, from the diversity and extent of the operations of man, rather than from an inspection of his organs, of which we have only a partial view. And if corporeal perfection corresponds with spiritual, as there is reason to believe it does, man, as he is superior to other animals by understanding, so he likewise is by organization. Whence we may infer, that those animals, whose structure most nearly resemble that of men, ought to be considered as the most elevated in the scale.

12. Of all animals that are known to us, the polypus is one whose structure seems to be the most simple, and to come nearest that of plants. This extraordinary animal seems to consist altogether of stomach. His body and arms are composed of one and the same, bowel, whose composition is perfectly uniform. The best microscopes only discover in them an infinite number of small grains, which are tinged with the nourishment the animal feeds upon.

Can these grains be so many utricles Can they receive the aliment by immediate conduits, prepare it and transmit it to other vessels appointed to convey it into the channels of circulation Is there a circulation in the polypus

The different kinds of vessels which the first conjecture supposes, and which their fineness or transparency may render invisible to must he lodged in the thick part of the texture of the polypus.

We are induced to think so from the experiment of turning it inside out, which being effected, does not cause any change in the vital functions.

But of what service can that property be to the polypus, which it cannot make use of without the assistance of man I mean the opera lion of turning the inside outwards.

I answer. that this property is one of the consequences of an organization peculiarly necessary to the polypus. The Author of nature never intended to create an animal capable of being turned as we do a glove: but he designed to form an animal whose principal viscera were lodged in the thickest part of the skin, and which had power, is a certain degree, to escape various accidents to which the nature of its life unavoidably exposed it. Now, what naturally follows from this organization is, the being enabled to endure this shifting without occasioning its death.

13.  Those animals whose structure appear less simple than that of the polypus, multiply like him by slips.

These worms have a stomach, intestines, heart, arteries, veins, lungs an] organs of generation. If we look narrowly into the circulation of their blood, we shall perceive its continuance with the same regularity in all those parts which have been separated from the rest by cutting.

These worms bring us to treat of insects.

14.  Here we are introduced into a kingdom of animals, the most extensive and diversified of any on the surface of the globe. That province of this vast empire which is seen on the surface of vegetables, is sufficient of itself to attract the curiosity of a traveller, either from the prodigious number of its inhabitants, or the singularity and diversity of their forms.

These are pigmies, the greatest part of which are so minute, as not to be distinctly seen without the help of a microscope. They bear the general name of insects, and this name was given to them on account of the incisions of various depths, by which the bodies of several of then) are divided.

The character which seems essentially to distinguish insects from other animals is, that they have no bones. The analogous parts with which some species of them are provided, are placed on the outside of their bodies, whereas, in other animals, the bones are always on the inside.

Life, in insects, does not result from a mechanism as compounded as in the animals of a larger size. In them, the number of different kinds of organs is smaller: but some of these organs seem more multiplied.

Considered in their exterior form, insects may be divided into two classes. The first comprehends insects, improperly so called, whose body is continued; these bear the general name of worms. The second class comprehends insects, properly so termed, whose body is divided by certain incisions or contractions.

In the greater part of insects of this class, the incisions separate the body into three principal parts: the head, the stomach, the belly : this division has relation to that observed in great animals. Some of the insects of the first class are without legs: others are furnished with them. All the insects of the second class have legs ; but some are winged, others not.

There is such a diversity in insects, that it may be questioned if there be not united in them every variety to be met with throughout the animal world. And what renders this variety still more surprising is, that it does not extend merely to the whole species, but likewise to individuals. The same insect has at one time organs that are not to be found in him at another. The same individual which in his youth belonged to the first class, in a more advanced age takes up his rank in the second. From thence arise the difficulties attending a proper distribution of these little animals.

15.  The bodies of almost all insects are formed of a collection of rings, set in each other, which, by contracting or dilating, lengthening or shortening, contribute to all the motions of the animal.

The head, in many species, changes its form in an instant, It contracts and dilates itself, lengthens and shortens, appears and disappears, at the pleasure of the insect. The flexibility of its folds enables it to make these motions. In other species, the head is in one constant position, and bears a greater resemblance to that of the larger animals, by the hardness of its covering, which is scaly.

The mouth is sometimes discovered to be a simple circular aperture: but it is generally furnished with hooks, or a kind of pickaxe; with teeth, or two indented shells which they move horizontally; with a trunk, a very compact instrument, which serves to extract and liquefy, and raise up alimentary juice; or with a sting, which is an organ analogous to the trunk, and endued with the same essential functions.

Several species have two of those instruments united in them, sometimes the teeth and the trunk, and sometimes the trunk and the sting. Many species of insects are deprived of the use of sight. With them the feeling, or some other sense, supplies the defect of eyes.

The eyes of insects are of two kinds: the smooth ones are always few in number: the rough commonly amount to several thousands, ,and are fixed on the sides of the head, in the form of two semicircular masses. In both of them they are utterly immoveable.; and. their number compensates in some measure the want of mobility: it is therefore less a mark of perfection than of imperfection. Many species have at the same time two smooth eyes and two rough ones.

Hearing seems to be denied to insects; at least the existence of this sense in them is very doubtful.

The case is not the same with respect to smelling. Divers insects have it in an exquisite manner, but the seat of it is not known. May it not be situate in those two moveable horns, called the antenna, whose use we are yet unacquainted with

The legs of insects are scaly and membraneous. Those are moved by the assistance of divers articulations, while these, which are more pliable, are turned every way without difficulty. These two sorts of legs are often united in the same worm. Some of them have several hundred legs; but do not on that account walk faster than such as have only six.

The wings, which are two or four in number, are sometimes formed of a simple and more or less transparent gauze, and sometimes covered with little scales differently figured; in some they are composed of feathers, as in birds ; in others they are covered, or enclosed in cases. In many species the male is winged, and the female not.

On the sides or extremities of the body are little oval apertures. shaped like the ball of the eye, and susceptible of the same motions. These are so many mouths for the purpose of respiration.

16.  The interior part of insects contains four principal viscera:

the spinal marrow, the intestinal bag, the heart and the tracheal arteries.

A blackish thread, which is extended the whole length of the belly from the head to the hinder part, and knit together at certain distances. is the spinal marrow of insects. or the principal trunk of the nerves.

The knots placed from one space to another, seem so many particular brains, appointed to distribute the nervous strings to the neighbouring parts, from the action of which the feeling and motion proceed. The first of these knots constitutes the brain, properly so called.

On the medullary thread is placed the intestinal bag, which is equal to it in length. It is a long gut, in which are contained the aesophagus, the stomach and intestines.

Along the back, and parallel to the intestinal bag, there runs a long and thin vessel, in which may be perceived, through the skin of the insect, alternate contractions and dilatations. This is the heart, or that part which performs the functions of it.

The arterial vessels of insects perfectly resemble those of plants. There is in every part of them the same structure, colour, elasticity, destination, and dispersion through the whole body.

 17.  Worms, whose bodies are lodged in a crustaceous or stony seem to constitute the connexion between insects and shellfish

There are notwithstanding some shell animals, whose structure with respect to its simplicity, seems to vie with that of the polypus.

Of this number is the pond muscle wherein we can discover neither spinal marrow, arteries, veins -nor lungs.

Does the scale of nature branch out as it advances May insects and shell-fish be two parallel branches of this great stem May the frog and the lizard, which bear so near a resemblance to insects, be a ramification of them We are not able at present to answer these questions.

Such is the gradation between beings, that they often differ from each other by slender shadowings; and such is the narrowness of our capacities, that none but the plain and more striking marks attract our notice.

18. The agreeable diversity in the figures of shells, helps us to judge of the variety subsisting in the organization of those animals who are the inhabitants and architects of them. Some consist of one entire piece; others of two or more. Some are formed in imitation of a trumpet, a screw, a tiara, a dial. Others resemble a helmet, a club, a spider, a comb. In this, it is a kind of fleshy case ; in another it is a ship, wherein the sailor is at the same time rudder, mast, and sail.

Animals that have shells, and insects with scales, seem to have an affinity to each other by a common character; both of them have their bones placed on the outside. We may in effect consider the shell as the bone of the animal which occupies it; since he brings it into the world with him, and adheres to it by different muscles.

But it is certain that most shells are formed of the stony juices, which transude from the pores of the animal.

The bones, as well as the shells of insects, grow and are nourished by vessels which pass through their substance.

Shell-fish form two great families, that of the conche, or larger kind, whose shell is made up of two or several pieces; and that of snails, whose shell consists of one single piece, turned for the most part spirally.

The stucture of the first seems much more simple than that of the last. The concha have neither head, horns, nor jaws; one can only observe in them air vents, a mouth, an anus, and sometimes a sort of foot. The greatest part of snails, on the contrary, have a head, horns, eyes, a mouth, an anus, and a foot. The round and fleshy head is at the anterior and upper part of the animal. It contains a brain, composed of two little globes, whose apparatus is of such a moveable nature that it is transferred from the hinder to the fore part, at the pleasure of the snail. The horns, which are two or four in number, placed on the sides of the head, are a kind of pipes, susceptible of various motion, and which the animal can draw into his head by the help of a muscle which the Grand Observer has ordained to perform the functions of the optic nerve. In some species of snails, the eyes are placed at the extremity of the horns, as at the end of the shank of a pair of spectacles. In others at the base, or towards the middle. They are black and brilliant, pretty much resembling the form of a very small onion We can only discover their tunic, which is called the urea; but they have the three humours belonging to our eye. The mouth, which it commonly a small chink, like a furrow, is furnished in many species of them, with two cartilaginous jaws placed on each other, whose inequalities or clefts perform the office of teeth ; some species have, real teeth, like those of a sea-dog, which are extremely small.

The shell-fish that have no jaws, have a fleshy or muscular pipe, which supplies the place of a snout.

Snails are not provided with feet; but they have one foot of a particular make, which is nothing more than a collection of a great number of muscles, whose motions imitate those of the waves of the sea. A pretty thin membrane lines the inside of the shell, and sometimes the-outside. It is a kind of mantle, furnished with trachea or air vents, which separate the air from the water, at the origin of which are perceived little gills destined to the same uses. The heart, which is situated near the surface of the body, has a sensible motion, whereby it. raises and falls alternately In the concha it is underneath the stomach.

19. Animals with shells bear an affinity to fishes. Reptiles seem to take place between or next to them, being united to shelled animals by the slug, and to the fishes by the water serpent.

In reptiles, animal perfection begins to increase in a sensible manner. The number of their organs, their conformation and exercise give them, on this account, a greater analogy with the mechanism of those animals we esteem the most perfect. The organs of vision, hearing, and circulation, furnish examples sufficient to indicate -this. This analogy is augmented in fishes.

The eel by its formation, and creeping fishes by their method of moving, connect fishes with the water serpent.

20. Fish, like reptiles, are for the most part covered with scales, whose figure and rich colours help to make a distinction between the species.

There is a great variety in the form of fishes. Same are long and slender; others are broad and short. We see among them, flat, cylindrical, triangular, square, and circular ones. Some are armed with a great horn. Others wear a long sword, or a kind of saw. A third sort are furnished with pipes, through which they throw out the remainder of the water they have swallowed. Wings are to birds of the same use as fins to fishes. Some have two or three: others have a greater number. The head of fishes, like that of reptiles, is joined close to the body. The mouth, which is commonly furnished with two or more rows of teeth, is sometimes placed on the back. aw are the eyes. The lungs, which are formed of several blades, of vascular leaves, are often placed at the surface of the body. They are known by the name of gills. But let us avoid anatomical descriptions, which would carry us too far. We shall now confine ourselves to some of the principal varieties, and to the sources of those relations that are more striking.

21. I see the flying-fish dart itself into the air from the bottom of the water, having fins resembling the wings of a bat. Herein it has an affinity to birds. But I see a great animal advancing towards the seashore, having a bead and fore part like a lion, and the hind part resembling that of a fish. It has no scales; and is borne on two paws, that have toes with fins to them. It is called the sea-lion He is followed by the sea-calf, and the hippopotamus or sea-horse, and by all in general of the cetaceous kind. The crocodile and tortoise present themselves to my view in their turn; and I now find myself among quadrupeds. Without presuming to account for the ways of nature, we wifi at present place birds between fishes and four footed animals. In this order aquatic birds are ranged immediately under the flying-fish. Amphibious birds, or such as live both on land and in the water, will occupy the scale next in course, and by this means open a communication between the terrestrial, aquatic, and aerial regions.

To this new mansion there is added a new decoration. To scales succeed feathers, which are closer compacted and more varied: a bill takes place of teeth; wings and feet are to them instead of fine; lungs formed within, and a different structure, cause the gills to disappear a melodious song follows a profound silence. Between the cormorant and swallow, the partridge and vulture, the hummingbird and ostrich, the owl and peacock, the raven and nightingale, what a surprising variety is there of structure, proportion, colour, and song

22. I-laity birds, having projecting ears, a mouth furnished with teeth, and whose body is carried on four paws armed with claws, are they birds in reality! Are quadrupeds, that fly by the assistance of great membranous wings, really such the bat and flying-squirrel, are these strange animals, which are so proper for establishing the gradation that subsists between all the productions of nature. The ostrich with the feet of a goat, which rather runs than flies, seems to be another link which unites birds to quadrupeds.

The class of quadrupeds is not inferior in variety to that of birds. These are two perspectives of a different taste, but which have some analogous point of view. Carnivorous quadrupeds answer to birds of prey. Quadrupeds that live on herbs or seeds, answer to birds that live on the same kind of aliment. The screech owl among birds is the same as the cat among four footed animals. The beaver seems answerable to the duck. Quadrapeds may be divided into two principle classes. The first comprehends quadrupeds with a solid foot.  The second comprises quadrupeds whose feet are furnished with claws toes. Amongst quadrupeds of the first class, from the stag to the and those of the second, from the lion to the mouse, what a diversity models, sizes, and motions, do we observe!

By what degrees does nature raise herself up to man

How will she rectify this head that is always inclined towards the earth How change these paws into flexible arms What method will she make use of transform these crooked feet into supple and skillful bands Or how will she widen and extend this contracted stomach In what manner will she place the breasts, and give them a round suitable to them

The ape is this rough draught of man: this rude sketch, an imperfect representation, which nevertheless bears a resemblance to him and is the last creature that serves to display the admirable progressive - of the works of God.

Chapter 4 - Continuation of the Gradual Progression of Beings