ePub 版

sects, the greater number seem to be as little allied to she vegetable kingJoni, as oiber animals, it must, however, be consessed, that tUere are fume, which, in external appearance, or in some other respect, appear to have a nearer relation to it. Such, for instance, are the lea anemones (afania) which have rather the sigure of a sungus, than of an animal, and which stir so little from the stone they adhere to, that one would think they were rooted in it. Not tltat they are incapable of progressive motion; bat, it is so slow, as to be almost imperceptible, and they hardly move over a space of half an inch in a quarter of an hour.

Such, likewise, is the semale of thole animals, called by Reaumur, gall-insects, and which have always been taken in Europe, for real galls. When the semale of this insect is with young, she becomes incapable of changing place, she, loses the sigure of an animal, and assumes that of those excrescences, commonly called by the name of galls.

Such, likewise, is that specieli of tænia, or flat and artku1-ated worm of the human body, whose head has not been

observed, and which, it is said, is incapable of motion

Lastly, such is that animal, common in ditches, the form of which, has some resemblance to the seed of the dandelion, (Hydra polypus.)'

It is genera,ly sixed by its extremity, to some other body, without changing place, except very rarely. It has not the appearance of an animated being: if it is cut in two, and even into three parts, each part recovers, and assumes the sigure of the whole, and thus, there are two or three animals made out of one. The young issue from its sides,'by a fort of stow and insensible vegetation, and having grown in this manner, for a certain time, like brandies, and haTing, even themselves, pushed out young in the fame way, they are detached from the mother, and live apart. By the greater part of these circumstances, one could scarcely htsitate to rank it among common vegetables; but, when it ismore narrowly examined, we perceive, that, when the water around it is agitated, it contracts and draws itself in; then expands itself again, so that we begin to think it ought to bs classed above ordinary vegetables, and to be considered as a sensitive plant. But, upon still narrower inspection, from time to time, vihen we sind, that it is capable of voluntary motion, and that it does not always continue in the fame ipot, but that; it transports itself from oae place to a

nother. uother, by a motion, which, though very flow, is evident, that it even endeavours to get towards the places which arc most enlightened, that the beards which are placed round Us anterior extremity, surnisti it, by their viscidity, with the means of catching the small water insects that come in its way, that these beards serve it for arms to carry the insects to its mouth, and that afterwards it swallows them; we are sensible, that it is not enongh to place it with the sensitive plants, but that it must be acknowledged as a .true animal. Besides, the vegetable and animal kingdoms approach each other so nearly, by means of this equivocal being, that M. Trembley, a very attentive observer, and who had verisied the facts 1 have just mentioned, before me, was- not able, till after a diligent observation of it, for many months, to determine, that it was actually an animal.

Page 39,1. 21.

They are notsurni/bed ivith bones. This observation of the author, that insects are destitute of bones, appears to me pretty just: I even believe, that one of the best characters for distinguishing insects from other animals, would be their' want of an internal ikeleton. It cannot be denied, however, that, if insects have not bones, many of them have parts that answer the purpose of bones. The snail, for instance, has, within its body, according to Swammerdam, a stony tubercle, in which many of the nerves of that animal terminate. Caterpillars, and many other creeping insects have their head desended by a hard lhell-like covering, and often too, a similar part above their sirst ring or segment, many of the larvæ that change into beetles, and even the beetles themselves, the sea eggs, lobsters, crabs, &c. are vall armed with a stiell. Lepidopterous insects and all flies have the thorax hard enough to resist moderate pressure. The ichneumons in general, have it very hard; 1 have seen some of these, whose thorax was so hard, that it bent very strong pins I wanted to pierce them with. These parts, however, differ from true bones. 1. By being rather flielllike, stony or crustaceous, than osseous. 2. By being placed, (except in the slug) oa the outside of the body, and not in the inside. 3. By lieiii^ sunned in many, if not in all insects, not by a sap which circulates in these stiells, but by a simple apposition of particles, which transpire from the body of the animal, and afterwards crow hard. 4. By these.

shells shells being apparently given for a covering or desence.— And 5. By their being so little essential to the internal construction of the body of insects, that it is in a manner demonstrated, that the covers of ihcll sish, are loosened, whenever their enlargement requires that the muscles they are attached by change their place \ it is also certain, that many osten cast their shells, and that a great number of those that are Best armed, exist and act all the time which has preceded their ultimate transformation, without having had any thing of the kind on their body. It would seems therefore, that the name of bone, cannot be given, with propriety, to those shells or crustaceous coverings. Indeed) this matter is liable to some difficulty, in the case of the flug. Its stony part has been bestowed on it, neither for a covering nor a desence. It seems to exist within the bodv, merely as a sixed point for the muscles to rest on, and to perform the sunction of a bone. However, when we consider on one lide, that this mass has less the form and substance of a bone, than it has of something lapideous; that besides, it is single in the body of the flug, and only occupies there, a very small space, while the bones, in every animal possessed of them, are found in great numbers, and form, almost always, a skeleton of connected pieces, which sup-i port, internally, the whole mass of the body, it does not appear, that this singularity, which takes place in the flug, is sufficient to make it an exception to the rule. 1 make the same observation, with respect to those cartilaginous parts, which are sound internally attached to the calcareous covers of lobsters, and which they quit, when they cast their shells; being nothing but cartilages, and by no means true bones.

I know, that some curious observers, when tearing away from the leg of a flea, the hard part, which covers the articulation next the body, have thought they perceived a bone, in the place which the removal of the hard part had left bare; but I know likewise, that the leg of a flea is an object too small, to allow us to affirm, even with the aid of a" microscope, that what we there see, is a bone, and not a nerve, or rather, a part of the very substance of the leg. If there was a bone in the leg of a flea, we should much father expect to sind it in the leg of some larger msect, especially among those whose legs resemble those of the flea/ as the grasshopper; but nobody has hitherto discovered any


[ocr errors]

riling like one in it. Add to this, that the legs of a fl?a being armed with hard (hells, it is not easy to conceive, of what use bones would be to them, these shells being alone more than sufficient for supporting the action of the nerves and muscles, and for preventing their limbs from folding between two articulations.

But if, after all, experiment, superior to any reasoning, should enable us to discover true bones in an infect, this singularity, which would approximate the structure of it to that of other animals, would not be sufficient to remove it from the class of insects; but, as it seems established in nature, that in every kind of created beings, whose extremw ties approach each other, there arc always limits which separate them, and that one of the chief, and most constant of those limits between infects and other animals, seems to be the internal skeleton given to the one, and not to the others, it would seem, that we cannot, without confounding the classes of beings really distinct, rank among infects, any animal, possessed internally of a skeleton formed by a contiguity of bones. 1 conclude, therefore, that this contiguity alone, is sufficient to exclude every aiimal in which it is founds from the number of infects.

Page 39,1. 27. .

Whose subjlance is net fiefi. What the author remarks here in pasting, to wit, that the substance of insects, properly speaking, is not flesh, may furnish a second mark for distinguishing insects from other animals, that is, that if we find an animal, whose substance does not resemble flesti, we may conclude, that it is an insect. But we must not carry this too far; we would fall into mistakes, were we to conclude, that an animal is not an insect, because it has a substance similar to flesh; for crabs, lobsters, and some other animals of the fame order have actually flesh, though they are undoubtedly insects. Besides, as the question is, how Insects are to be distinguished from all other animals, and consequently also, from sillies, it is evident, that the expressions, fl'Jh and bones, made use of by us, must be taken in a very extended sense, in order to comprehend the substance and bones of fishes.

[merged small][graphic]

red, and this is a third distinctive character. But1, as it 5s very rare to find in Natural History, any rules without exceptions, the rule that insects want red blood, suffers an exception, both in the earth worm, whose blood has a tinge of red, and in a certain shelled snail, very common in the ditches in Holland, whose blood is purple. Perhaps too, it jnay be thought another exception to the rule, that many fl es, when they are killed, produce large spots, of a very bright and deep red. But it must be remarked, that these are by no means the blood of the fly. When they were in the maggot state, nothing similar was to be observed in. them; and when changed into flies, this rid matter is not found in their bodies, as it ought necessarily to be, were it blood which circulates in their veins. It is only found in their eyes, where it assist;, moil probably the organ of sight. I know, that blood is sometimes remarked in the bodies of gnats, and of some flies; but, if we attend accurately to the circumstance, we shall find, that it is not to be found, except in the bodies of those gnats and flies, which fuck the blood of animals; and this blood will be found, only in their stomachs, or in their intestines: an evident proof, that this blood is that of the animals they attack, as the author has observed.

Page 40,1. if ,

If tve compare instils. Here is a fourth character, very useful as a distinguishing mark of insects; for though some of them equal, and even surpass in size, the smallest of the Other animals, it may, however, be said, considering things iri general, that, to descend from the greatest animals to the simllest, infects begin nearly where the others end.

To these sour characters, which respect the bodies of insects, as to substance and extension, we may add five others, which have a reference to their external form, and which are not less proper for distinguisliing insects from the other animals, than the preceding characters. The first is men» tjoned by Mr Lesser, and consists in this, that the bodies of the greater part of insects are, as it were, divided by incifcires, which has given rife to the name they bear. The second, is, that no insect without wings has only four feet, nor any flying infect but two. The third, that they have no visible nostril, or external ears: but, that they have their organs of respiration, either in their thorax or abdomen.


« 上一頁繼續 »