The fourth, that the organs of maftication, or the teeth of fuch as have any, act from right to left, and from left to right, and not up and down. Laftly, that their eyes are deftitute of eye-lids, and that they have neither iris nor pupil. Here, then, are nine characteristic marks, by which infects are difcriminated from all other animals. They are found in general, applicable to every infect. But there are many fpecies, which want one of the last mentioned eight characters. The number of those that want two of them is fmall; perhaps, there may be fome that want three of them; though I do not know any. If fuch were to be difcovered, I would make no difficulty in acknowledging them for infects; the first character, joined to five others, and even with four, would be fufficient. I would not venture to fay fo much, were the first character to be wanting, because that appears to me, the fundamental difcriminating character, that without which no animal can be confidered as an infect. But when, after having examined an animal, neither the first character, nor any of the other eight, which I have just mentioned, are found to belong to it, I think it would be, to confound with improper names, things which Nature has effentially diftinguifhed, were we to give such an animal the name of infect. Confequently, neither frogs, toads, ferpents, fnakes, vipers, tortoifes, lizards, crocodiles, nor other reptiles of that kind, can properly belong to the clafs of infects, although very able naturalifts have confidered them as fuch, perhaps for want of attending to the characters we have juft established. For those animals, far from poffeffing all thefe different characters, have few, if any of them. They have bones, which, in almost all of them, form a compleat skeleton: they have flesh and blood: the smallest of them are larger than the generality of infects; they have no fenfible incifures; thofe which have legs, have four; they breathe through noftrils; their maxillæ act perpendicularly, and the eyes of the greater part have eye-lids, an iris, and a pupil; in a word, they are in every respect, as fimilar to the larger animals, as they are different from infects.

But, it will be faid, if the animals I have named, belong not to the clafs of infects, to what clafs must they be referred? I answer, that as they differ in many refpects from infects, and in many other refpects from the reft of animals, and that thus, they cannot be claffed conveniently, under any

of the four established divifions of animals, I would make no difficulty in forming them into a clafs by themselves, which might be called, for want of a more fuitable appellation, the class of reptiles, taking the word, in a sense a little lefs vague than that which it generally has; fo that, according to this idea, all the lower animals might be divided into five general claffes, to wit, quadrupeds, birds, fishes, reptiles, and infects.

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The hydra, the crocodile. The author, by oppofing the hydra and crocodile, to infects, fhews, that he did not confider the reptiles we have been speaking of, as belonging to the clafs of infects.

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According to Leuwenhoeck. This writer goes ftill farther, and affirms, that he had found, in the feminal fluid of dif ferent animals, fuch minute animated beings, that a million of them, and fometimes ten millions, would be required to equal the size of a grain of fand. Neither is that all. M. de Malezieux pretends, that he had observed with his own microscope, animals, feven and twenty millions of times fmaller than a mite. Hift. of the Royal Acad. of Sciences. 1718.

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The fkin of infects is different. As the skin of insects, like that of other animals, varies exceedingly, and as in the one, as well as in the other, fome have it foft, hard, rough, fmooth, thick, thin, downy, fpiny, &c. it does not appear to be in the quality of the fkin, that the characters proper for diftinguishing infects from other animals are to be fought, but rather perhaps in the divestment of that fkin; for it is remarkable that quadrupeds, birds and fishes, never quit their fkins, and that the greater part of infects, as well as reptiles, change theirs often.

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Compofed of feveral rings. Among infects, fome are found that have neither rings nor incifures, fuch as fnails, Augs, &c. but fuch make but a very small part,

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Deeper than thofe of the lobfter. It would feem here, that

M. Leffer

M. Leffer does not confider the lobfter as an infect. But as that animal has no internal fkeleton, as it has its body divided by incifures, as it has neither red blood, nofe, ears, nor mouth, nor eyes, fimilar to those of the other animals, but, as in all these respects it resembles infects, I think we cannot hesitate in fixing it in this clafs, although in size, it greatly surpasses the generality of infects.

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They have not exactly. If the perfection of an animal were to depend on the number of its external and internal parts, the comparifon, which, in this refpect, might be made between infects and other animals, could not fail of turning to the advantage of the former; of this the reader will find convincing proofs in the courfe of this treatise.

Of the divifion of infects. It is not fo eafy as one would imagine, to form a proper division of infects. It is not fufficient to find out fome diftinctive differences between fpecies and fpecies, and of thefe to make fo many orders, without troubling ones felf, about their being more or less effential or accidental: the divifions must be founded on the very nature of the things, otherwife, they will be more apt to darken, than to illuminate the fubject. A moft wonderful order prevails throughout all Nature, compofed of diverfities and analogies without number. It is this order that we muft endeavour to discover and to follow; it is on the just perception of these diversities and analogies, that we must found the general and particular divifions of every fubject in Natural Hiftory. But this is a task very difficult to fulfil, and without knowledge acquired by long application, it is not eafy to accomplish it: accordingly, there are but few naturalifts, who have attempted to give us a fyftematic divifion of infects. I am acquainted, only with thofe of Valif neri, Swaminerdam, Linnæus, and our author. I fhall take the liberty of making a few obfervations on each of thefe fyftems.

I. Valifneri divides infects into four claffes, drawn from the places they are found in. The first clafs comprehends, thofe infects which live on plants; the fecond, fuch as live in water or other fluids; the third, thofe that live within the earth, or among terreftrial and ftony fubftances: and the

Q ૧ 2

laft

laft, thofe which live on other animals, or in their bodies. But this divifion is faulty, in being taken from characters that are rather accidental than effential to infects; and this has made him fall into another much more important error; that of reverfing the order of Nature, by comprehending, in one and the fame clafs, infects which have no other relation to one another than that of being found in the fame places, while it feparates infects which, on account of their effential analogies, ought naturally to have been united. Add to this, that in following the fyftem of Valifneri, we would often find ourselves at a lofs to know, in what clafs to place certain infects, either because they live indifferently in many places, like the onifci, earwigs, and millepieds, which live equally on plants, and among earthy and ftony fubftances, and which, confequently, ought at once to belong both to the first and third clafs; or because there are others, which, at different periods of their life, live fucceffively in different places. Such are many fpecies of beetles, which live as larvæ in the waters, transform themselves into nymphs in the earth, and afterwards inhabit indifferently, either the water or the air: fuch are many other beetles, and other coleopterous infects, which live firft in the earth, then on plants and fuch likewife are the dragon flies, the ephemeræ, gnats, and many different forts of flies, and even fome butterflies, which live firft in the water, then in the air, on plants, or animals, and among which are to be found fome, that before mounting into the air, have undergone their transformations in the earth. All these infects, and many others, confidered according to the different periods of their life, would, in the fyftem of Valifneri, be fometimes of one clafs, and fometimes of another, and fometimes indeed, in three of the claffes at once, which could not but cause a deal of confufion, and which besides, renders his fyftem impracticable.

II. The general divifion of Swammerdam feems much better imagined. He diftributes all iniects into four claffes, the distinctive characters of which are taken from the nature of the animals themfelves. The firft comprehends. thofe which are fubject to no change of form, and the three others are founded on their different modes of transformation into nymphs and chryfalids. M. Leffer explains them in his VII. chapter, and I fhall therefore difpenfe with detailing them here. I fhall only remark, that the great

4

defect

defect in his fyftem is, that the fourth clafs feparates from the third, animals of the fame kind, and which have a much greater refemblance to one another, than those of different kinds, that conftitute his third class. For while the third clafs is compofed of lepidopterous infects, of beetles and flies, animals exceedingly diftinct from one another, the fourth confifts only of flies which are not comprehended in the third. Thus, flies which are animals of one genus, are found feparated, and diftributed into different claffes, while butterflies and beetles, animals of different kinds, are found united in the fame clafs. This is certainly a very great defect, and it is further augmented, by Swammerdam's introducing into his fourth clafs, feveral fies, which, according to his own principles, ought naturally to have been ranged in the third.

Befides, as the state of chryfalis and nymph is, with infects, generally a ftate of weakness, and always of imperfection, and as moreover, it is the ftate under which they are the leaft known, and often with moft difficulty found, because then they are for the most part enveloped in a cone, or hid in the earth, or in places where it is not easy to find them. I am of opinion, that this ftate is not a proper one for furnishing fuch diftinctive marks as can be of any utility.

III. Linnæus, in his Syftema Naturæ, divides infects into feven general claffes. In the first clafs, he places all those which have covered wings, as the different forts of beetles in the fecond, thofe that have naked wings, fuch as butterflies, dragon-flies, ephemeræ, wafps, ichneumons, and other flies. In the third, thofe which he names half-winged, the character of which is, that they have not all wings, and have no covers to them: in this clafs he enumerates crickets, grafshoppers, ants, bugs, scorpions. His fourth clafs comprehends infects that have no wings but limbs, as the loufe, the flea, the fpider, the lobfter, the onifcus, and the millepied. The fifth includes the creeping infects, whole body is naked, and deftitute of limbs, as the tenia, the earthworm, the leech, the flug. The fixth contains both land and fea fhelled animals, and his seventh and last, such as he names zoophytes, furnished with limbs, fuch as the echinus, fepia, fea ftars, &c.

[*As the fyftem here alluded to, was what Linnæus publifhed in the firft edition of his Syftema Naturæ, and which

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