by Aristotle
In the Testacea the presiding seat of sensation is in a corresponding position, but is less easily made out. It should, however, always be looked for in some midway position; namely, in such Testacea as are stationary, midway between the part by which food is taken in and the channel through which either the excrement or the spermatic fluid is voided, and, in those species which are capable of locomotion, [682a1] invariably midway between the right and left sides.
In Insects the organ which is the seat of sensation, lies, as was stated in the first treatise, between the head and the cavity which contains the stomach. In most of them it consists of a single part; but in others, for instance in such as have long bodies and resemble the centipede, it is made up of several parts, so that such insects [5] continue to live after they have been cut in pieces. For the aim of nature is to give to each animal only one such dominant part; and when she can, she makes it a unity; when she cannot, a plurality. This is much more clearly marked in some insects than in others.
The parts concerned in nutrition are not alike in all insects, but show considerable diversity. Thus some have what is called a sting in the mouth, which is [10] a kind of compound instrument that combines in itself the character of a tongue and of lips. In others that have no such instrument in front there is a part behind the teeth that answers the same sensory purposes. Immediately after the mouth comes the intestine, which is never wanting in any insect. This runs in a straight line and [15] without further complication to the vent; occasionally, however, it has a spiral coil. There are, moreover, some insects in which a stomach succeeds to the mouth, and is itself succeeded by a convoluted intestine, so that the larger and more voracious insects may be enabled to take in a more abundant supply of food. More peculiar [20] than any are the Cicadae. For here the mouth and the tongue are united so as to form a single part, through which, as through a root, the insect sucks up the fluids on which it lives. Insects are always small eaters, not so much because of their diminutive size as because of their cold temperament. For it is heat which requires sustenance; just as it is heat which speedily concocts it. But cold requires no [25] sustenance. In no insects is this so conspicuous as in these Cicadae. For they find enough to live on in the moisture which is deposited from the air. So also do the Ephemera that are found about the Black Sea. But while these latter only live for a single day, the Cicadae subsist on such food for several days, though still not many.
[30] We have now done with the internal parts of animals, and must therefore return to the consideration of the external parts which have not yet been described. It will be better to begin with the animals we have just been describing, rather than from the point at which we left off, so that proceeding from these, which require less discussion, our account may have more time to spend on the perfect kinds of animals, those namely that have blood.
[35] 6 · Insects, though they present no great multiplicity of parts, are not without diversities when compared with each other. They are all many-footed; the [682b1] object of this being to compensate their natural slowness and frigidity, and give greater activity to their motions. Accordingly we find that those which, as the centipedes, have long bodies, and are therefore the most liable to refrigeration, have also the greatest number of feet. Again, the body in these animals is insected—the [5] reason for this being that they have not got one vital centre but many—and the number of their feet corresponds to that of the insections.17
Should the feet fall short of this, their deficiency is compensated by the power of flight. Of such flying insects some live a wandering life, and are forced to make long expeditions in search of food. These have a body of light weight, and four [10] wings, two on either side, to support it. Such are bees and the insects akin to them; for they have two wings on each side. When, however, such insects are of very small bulk, their wings are reduced to two, as is the case with flies. Insects with heavy bodies and of stationary habits, though not polypterous in the same way as bees, yet have sheaths to their wings to maintain their efficiency. Such are the Melolonthae [15] and the like. For their stationary habits expose their wings to much greater risks than are run by those of insects that are more constantly in flight, and on this account they are provided with this protecting shield. The wing of an insect has neither divisions nor shaft. For it is no wing at all, but merely a skin-like membrane that, owing to its dryness, necessarily becomes detached from the surface of the [20] body, as the fleshy substance grows cold.
These animals then have their bodies insected, not only for the reasons already assigned, but also to enable them to curl round in such a manner as may protect them from injury; for such insects as have long bodies can roll themselves up, which would be impossible were it not for the insections; and those that cannot do this can yet draw their segments up and so increase the hardness of their bodies. This can be felt quite plainly by putting the finger on one of the insects, for instance, known as [25] dung-beetles. The touch frightens the insect, and it remains motionless, while its body becomes hard. The division of the body into segments is necessary; for that they have several controlling sources is a constituent of their substances, and is a character which approximates them to plants. For as plants, though cut into pieces, [30] can still live, so also can insects. There is, however, this difference between the two cases, that the portions of the divided insect live only for a limited time, whereas the portions of the plant actually attain the perfect form of the whole, so that from one single plant you may obtain two or more.
Some insects are also provided with another means of protection against their enemies, namely a sting. In some this is in front, connected with the tongue, in [35] others behind at the posterior end. For just as the organ of smell in elephants answers several uses, serving alike as a weapon and for purposes of nutrition, so does [683a1] also the sting, when placed in connexion with the tongue, as in some insects, answer more than one end. For it is the instrument through which they derive their sensations of food, as well as that with which they suck it up and bring it to the mouth. Such of these insects as have no anterior sting are provided with teeth, which serve in some of them for biting the food, and in others for its prehension and [5] conveyance to the mouth. Such are their uses, for instance, in ants and all the various kinds of bees. As for the insects that have a sting behind, this weapon is given them because they are of a fierce disposition. In some of them the sting is lodged inside the body, in bees, for example, and wasps. For these insects are made for flight, and were their sting external and of delicate make it would soon get [10] spoiled; and if, on the other hand, it were of thicker build, as in scorpions, its weight would be an incumbrance. As for scorpions that live on the ground and have a tail, their sting must be set upon this, as otherwise it would be of no use as a weapon. Dipterous insects never have a posterior sting. For the very reason of their being [15] dipterous is that they are small and weak, and therefore require no more than two feathers to support their light weight; and for the same reason their sting is in front; for their strength is not sufficient to allow them to strike efficiently with the hinder part of their body. Polypterous insects, on the other hand, are of greater bulk and hence have more wings and are stronger in their hinder parts. Now it is better, when possible, that one and the same instrument shall not be made to serve several [20] dissimilar uses; but that there shall be one organ to serve as a weapon, which can then be very sharp, and a distinct one to serve as a tongue, which can then be of spongy texture and fit to absorb nutriment. Whenever, therefore, nature is able to provide two separate instruments for two separate uses, without the one hampering the other, she does so, instead of acting like a coppersmith who for cheapness makes [25] a spit and lampholder in one. It is only when this is impossible that she uses one organ for several functions. The anterior legs are in some cases longer than the others, that they may serve to wipe away any foreign matter that may lodge on the insect’s eyes; for their sight is not very distinct owing to the eyes being made of a [30] hard substa
nce. Flies and bees and the like may be constantly seen thus dressing themselves with crossed forelegs. Of the other legs, the hinder are bigger than the middle pair, both to aid in walking and also that the insect, when it takes flight, may spring more easily from the ground. This difference is still more marked in such insects as leap, in locusts for instance, and in the various kinds of fleas. For these first bend and then extend the legs, and, by doing so, are necessarily shot up from [683b1] the ground. It is only the hind legs of locusts, and not the front ones, that resemble the steering oars of a ship. For this requires that the joint shall be deflected inwards, and such is never the case with the anterior limbs. The whole number of legs, including those used in leaping, is six in all these insects.
[5] 7 · In the Testacea the body consists of but few parts, the reason being that these animals live a stationary life. For such animals as move much about must of necessity have more numerous parts than such as remain quiet; for their activities are many, and the more the movements the greater the number of organs required to effect them. Some species of Testacea are absolutely motionless, and others not [10] quite but nearly so. Nature, however, has provided them with a protection in the hardness of the shell with which she has invested their body. This shell, as already has been said, may have one valve, or two valves, or be spiral. In the latter case it may be either helical, as in trumpet-shells, or spherical, as in sea-urchins. When it [15] has two valves, these may be gaping, as in scallops and mussels, where the valves are united together on one side only, so as to open and shut on the other; or they may be united together on both sides, as in the razor-fish. In all cases alike the Testacea [20] have, like plants, the head downwards. The reason for this is, that they take in their nourishment from below, just as do plants with their roots. Thus the under parts come in them to be above, and the upper parts to be below. The body is enclosed in a membrane, and through this the animal filters fresh water and absorbs its nutriment. In all there is a head; but none of the parts, excepting this recipient of food, has any distinctive name.
[25] 8 · All the Crustacea can crawl as well as swim, and accordingly they are provided with numerous feet. There are four main genera, viz. the crayfish, the lobsters, the prawns, and the crabs. In each of these genera, again, there are numerous species, which differ from each other not only as regards shape, but also [30] very considerably as regards size. For, while in some species the individuals are large, in others they are excessively minute. The crabs and crayfish resemble each other in possessing claws. These claws are not for locomotion, but to serve in place of hands for seizing and holding objects; and they are therefore bent in the opposite direction to the feet, being so twisted as to turn their convexity towards the body, [35] while their feet turn towards it their concavity. For in this position the claws are best suited for laying hold of the food and carrying it to the mouth. The distinction [684a1] between the crayfish and the crabs consists in the former having a tail while the latter have none. For the crayfish swim about and a tail is therefore of use to them, serving for their propulsion like the blade of an oar. But it would be of no use to the crabs; for these animals live habitually close to the shore, and creep into holes and [5] corners. In such of them as live out at sea, the feet are much less adapted for locomotion than in the rest, because they are little given to moving about but depend for protection on their shell-like covering. The Maiae and the crabs known [10] as Heracleotic are examples of this; the legs in the former being very thin, in the latter very short.
The very minute crabs that are found among the small fry have their hindermost feet flattened out into the semblance of fins or oar-blades, so as to help the animal in swimming.
The prawns are distinguished from the crabs by the presence of a tail; and from the crayfish by the absence of claws. This is explained by their large number of feet, [15] on which has been expended the material for the growth of claws. Their feet again are numerous to suit their mode of progression, which is mainly by swimming.
Of the parts on the under surface, those near the head are in some of these animals formed like gills, for the admission and discharge of water; while the parts [20] lower down in the female crayfish are more laminar than in the males, and in the female crabs the flap is furnished with hairier appendages. For the females retain their eggs in these parts instead of letting them go free, as do fishes and all other oviparous animals; for the appendages are broader and provide more room for the [25] eggs. In the crayfish and in the crabs the right claw is invariably the larger and the stronger. For it is natural to every animal in active operations to use the parts on its right side in preference to those on its left; and nature invariably assigns each organ, either exclusively or in a more perfect condition, to such animals as can use it. So it is with tusks, and teeth, and horns, and spurs, and all such defensive and offensive [30] weapons.
In the lobsters alone it is a matter of chance which claw is the larger, and this in either sex. Claws they must have, because they belong to a genus in which this is a constant character; but they have them in this indeterminate way, owing to imperfect formation and to their not using them for their natural purpose, but for [684b1] locomotion.
For a detailed account of the several parts of these animals, of their position and their differences, those parts being also included which distinguish the sexes, reference must be made to the Anatomies and to the History of Animals. [5]
9 · We come now to the Cephalopoda. Their internal organs have already been described with those of other animals. Externally there is the trunk of the body, not distinctly defined, and in front of this the head surrounded by feet, which [10] form a circle about the mouth and teeth, and are set between these and the eyes. Now in all other animals the feet, if there are any, are disposed in one of two ways; either before and behind or along the sides, the latter being the plan in such of them, for instance, as are bloodless and have numerous feet. But in the Cephalopoda there is a peculiar arrangement, different from either of these. For their feet are all placed at what may be called the fore end. The reason for this is that the hind part of [15] their body has been drawn up close to the fore part, as is also the case in the spiral Testacea. For the Testacea, while in some points they resemble the Crustacea, in others resemble the Cephalopoda. Their earthy matter is on the outside, and their fleshy substance within. So far they are like the Crustacea. But the general plan of [20] their body is that of the Cephalopoda; and, though this is true in a certain degree of all the Testacea, it is more especially true of those turbinated species that have a spiral shell. For18 both classes have this nature; and that is why they walk evenly, [25] unlike quadrupeds and men. Now men have their mouth in their head, i.e. in the upper part of their body; next comes the gullet, then the stomach, then the gut which extends to the vent for the residue. That is the arrangement in the sanguinea, i.e. the head is followed by what is called the thorax and the parts about it; the remaining parts, such as the anterior and posterior limbs, having been superadded [30] by nature, to minister to these and for locomotion.
In the Crustacea also and in Insects there is a tendency to a similar arrangement of the internal parts in a straight line; the distinction between these groups and the sanguineous animals depending on differences of the external organs which minister to locomotion. But the Cephalopoda and the spiral Testacea have in [685a1] common an arrangement which stands in contrast with this. For here the two extremities are brought together by a curve, as if one were to bend the straight line until D came close to A. Such, then, is the disposition of the internal parts; and [5] round these, in the Cephalopoda, is placed the sac (in the octopus alone called a head), and, in the Testacea, the spiral shell which corresponds to the sac. There is, in fact, only this difference between them, that the investing substance of the Cephalopoda is soft while the shell of the Testacea is hard, nature having surrounded their fleshy part with this hard coating as a protection because of their [10] limited power of locomotion. For this reason, in both cl
asses the excrement is voided near the mouth; at a point below this orifice in the Cephalopoda, and in the spiral-shells on one side of it.
Such, then, is the explanation of the position of the feet in the Cephalopoda, and of the contrast they present to other animals in this matter. The arrangement, however, in the cuttlefish and the calamaries is not precisely the same as in the [15] octopus, owing to the former having no other mode of progression than by swimming, while the latter not only swim but crawl. For in the former six of the feet are above the teeth and small, the outer one on either side being the biggest; while the remaining two of the eight are below the mouth and are the biggest of all, just as the hind limbs in quadrupeds are stronger than the fore limbs. For it is these that [20] have to support the weight, and to take the main part in locomotion. And the outer two are bigger than the pair which intervene between them because they have to assist the lowermost pair in their office. In the octopus, on the other hand, the four central feet are the biggest. Again, though the number of feet is the same in all the Cephalopoda, namely eight, their length varies in different kinds, being short in the cuttlefish and the calamaries, but greater in the octopus. For in these latter the trunk of the body is of small bulk, while in the former it is of considerable size; and [25] so in the one case nature has used the materials subtracted from the body to give length to the feet, while in the other she has given to the growth of the body what she has first taken from the feet. The octopus then, owing to the length of their feet, can not only swim but crawl, whereas in the other genera the feet are useless for the latter mode of progression, being small while the bulk of the body is considerable. [30] These short feet would not enable their possessors to cling to the rocks and keep themselves from being torn off by the waves when these run high in times of storm; neither would they serve to lay hold of objects at all remote and bring them in; but, to supply these defects, the animal is furnished with two long proboscises, by which it can moor itself and ride at anchor like a ship in rough weather, and by which it can catch prey at a distance and to bring it to the mouth. They are so used by both [685b1] the cuttlefish and the calamaries. In the octopus the feet are themselves able to perform these offices, and there are consequently no proboscises. Some animals have suckers and tentacles as well as feet; and these have the same capacity and [5] structure as those plaited instruments which were used by physicians of old to reduce dislocations of the fingers. Like these they are made by the interlacing of their fibres, and they act by pulling upon pieces of flesh and yielding substances. For they encircle an object in a slackened condition, and when they are put on the stretch they grasp and cling tightly to whatever it may be that is in contact with their inner surface. Since, then, the Cephalopoda have no other instruments with [10] which to convey anything to themselves from without, than either feet, as in some species or proboscises as in others, they are provided with these to serve as hands for offence and defence and other uses.