tus. It is thus that, proceeding on fuppofition, it is easy to account for every phenomenon, even for the existence of things which have never exifted, as thofe philofophers have done, who have explained to us the way in which putrefaction engenders infects. I have perhaps at prefent imitated them, by founding, in the inftance of the Tenia folium, on facts, which, though pretty generally received are not on that account the more worthy of credit. I know at leaft that Vallifneri, has endeavoured to render them doubtful, and to maintain that the Tænia is nothing but a chain of worms called Vermes Cucurbitini, which are linked to one another, and thus form aggregately the figure of a fingle animal. The reafons he alledges have a good deal of plausibility, and seem so ftrong that at, prefent a perfon would be accufed of prejudice not to fubfcribe to his opinion. But I must own they have not entirely convinced me. The difficulties which have oc→ curred to me on the fubject, will induce me to neglect no opportunity of endeavouring to difcover the truth; and till I have examined the animal alive, which I fhall do if I can procure it, I know not whether I fhall adopt the opinion of that learned author, or continue of the contrary fide.

What has been faid fufficiently fhews that though it is probable that there may be infects which multiply naturally without the common procefs by which generation is accomplifhed, the fact is not yet demonftrated. But what may be advanced as a certain fact, though it has still more the appearance of a paradox is, that there are animals which can be made to multiply, and which in fact do multiply by art, without the common generative procefs, as we inall have occafion to fhew in the fequel.

PAGE 30, I. 14,

Ariftot. Hift. Anim.

Engendered by all forts of matter. L. 5. c. 19, Procreantur porro infecta, aut ex animalibus generis ejufdem - - - aut non ex animalibus, fed fponte; alia ex rore qui frondibus infudat; - - - item alia ex cæno et fimo putrefcente oriuntur: alia in lignis aut ftirpium, aut cæfis: alia in animalium pilis, alia in excrementis, aut jam excretis aut adhuc intra animal contentis. Add. Plin. Hift. Nat. L. 11, cap. 33.

PAGE 31, 31,
1.

The covered veffel did not contain any animals. To the exexperiments

periments of Rhedi, may be oppofed that made by Leewenhoek, which he relates in his letter of the 14th of July, 1680. He there fays, that he had heard various opinions on the generation of infects: that he had even learnt, that a certain author had maintained, that, if a veffel, containing water and flefh, were carefully fhut, no animal could be produced in it: that this had led him to try the experiment; that, having taken for this purpofe, two tubes of glafs, fhut at the bottom, he had filled them half full of pepper, and had poured on water, fo as to fill the glaffes about threefourths. It was rain water, recently fallen, and was received into a porcelaine jar, very clean, and which had not been made ufe of for ten years: that having hermetically fealed the top of one of thefe glaffes, and having left only a fmall opening in the other, he examined the water three days afterwards in the open tube, and discovered in it, a great number of very minute animalcules of different kinds, moving in all directions: that having, on the fifth day, broken off the end of the fealed tube, the air iffued with violence, and he difcovered in the water of this tube, a fpecies of globular animals, larger than the largeft of thofe in the other tube. Here, then, were animals generated, in a place clofely fhut, and where no infects could enter to depofite their eggs: which appears quite contrary to the experiments of Rhedi, and furnishes an argument in favour of equivocal generation. But, if we, attend to the anima's which make the fubject of thefe experiments, the difficulty will foon be removed. It is certain, that the experiments of Rhedi were made on thofe maggots that are of a fentible bulk, and which, without the aid of a magnifier, are every day feen in putrid animal fubftances. His object was to prove, contrary to the opinion of the antients, that thefe maggots were not produced by the corruption of the animal matter, but fprung from eggs which flies had laid in it; and this appeared clearly from the precautions he took to keep off the flies. He contented himfelf, with covering the mouth of the veffel with a thin clo h, a precaution which would have been ufclefs against infects, incomparably more minute, but which was fufficient to exclude common flies."

The experiment of Leewonhock, on the contrary, refpe&s animals of a quite different kind, animals, of which a vaft number may live in a Imall quantity of water: animals which he

calls

calls very minute, that is, in his ordinary ftile, animals, that it would require a million of, nay ten millions, and fometimes an hundred millions, to compofe the bulk of a grain of fand; in a word, animals which one would not suppose a microscope could make visible, had he not taken care to demonftrate its poflibility. We eafily fee, that the precauti ons which Leewenhoek took, to exclude fuch animals from the tube he had fealed, were by no means fufficient. These a nimals or their eggs, might have been, either among the pepper,or in the rain water he employed,or even in the air which filled the void in his tube: there was, therefore, nothing furprifing, in animals being found there, five days afterwards. To overturn, by his experiment, what had been proved by Redi's, Leuwenhoek ought, at leaft to have boiled the water and the pepper in the very tube, and then to have fealed it immediately. If he had then found, fome days afterwards, any animals in that water, his experiment would very much have difconcerted the modern naturalifts: but, I am perfuaded, that is what would not have happened.

PAGE 36, 1. 29.

From which fimilar infects are to be generated. This ingenious comparifon, which fhews the conformity of infects with plants, is fimilar to that made by Swammerdam, in the first part of his General Hiftory, where he compares the developement of the different orders of infects with the plant called the carnation. The greater animals may, in fome refpects, be likewise brought into the comparison of M Leffer, fince all, or at leaft, many of them, proceed likewife from an egg; that all of them increafe, by means of a nutritive fluid; and that in general, they do not propagate their kind, till they have attained their ultimate perfection. It muft, however, be confeffed, that fome of the analogies which our author difcovers between infects and plants, are but imperfect. That, for inftance, of the wings of infects with the leaves, feems a little far fetched; for, in the first place, the leaves appear, almoft as foon as the bud begins to open, while the wings of infects never make their appearance, till they have attained their perfect ftate. Secondly, The leaves grow flowly after being difengaged from their gems; but the wings of infects, after having quitted their covers, elongate themselves immediately, and acquire their full fize in a few minutes. Thirdly, the number of leaves in a plant is not fixed; they fall and are renewed, and this

PP

viciffitude

viciffitude lafts as long as the plant itfelf: but the number of wings in every different infect is invariable, and a wing once loft, can never be fupplied. Laftly, according to the conjectures of the most able botanists, the leaves are given to plants, to defend the root and the ftem from the heat of the Sun,to facilitate the evaporation of fuperfluous humidity, and to promote the circulation of the fap, which is to elaborate and prepare the fhoots, the fruit and the feeds; while the wings are beftowed on infects, for a very different purpole, to wit, to facilitate their motion from place to place. Be. fides, if the wings of infects in general, refembled what is faid of thefe of a certain Indian infect, called in that coun try, the walking leaf, (Cicada foliacea; Gryllus ficcifolius,) their analogy with the leaves of plants, or at least of trees, would be more remarkable. The wings of thefe infects, not only in the form and nerves of the wings, refemble the leaves of trees, but in their colour. I have feen fome of them with wings of a bright green, others, with wings of a darker green, and like that of a leaf at full growth, and o thers of the colour of a withered leaf. It is faid, that their wings are of the first colour in fpring, of the fecond in fummer, and of the laft in autumn; that afterwards, they fall, and that the infect remains without wings during the winter, and that they fhoot forth again in the fpring. If all thefe circumstances were true, we could not deny, but that the wings of this infect had a very marked analogy with the leaves of trees; but, at the fame time, we must allow, that in this refpect, it differs from other infects, and is probably unique in its kind; at least, there is not, fo far as I know, any other, whose wings are liable to the fame viciffi tude.

In fine, it may be observed, that the comparifon made by the author, between a nymph or chryfalis, from which a perfect animal iffues, and a flower-bud, which produces fruit in its maturity, exceeds fomewhat, the terms of the parallel in question. His object was to fhew the analogy between infects and plants. For this purpose, the author compares the egg of an infect to the feed of a plant, its body to the ftem, and its wings to the leaves. It would be neceffary, in order to compleat the analogy, to compare fome other part of the infect with the flower-bud, but not to compare with it, the entire infect, as he has here done.

PAGE 37, L. 4.
1.

On which they are placed. If Mr Leffer was content, in

this place, with inftancing only one mark of conformity between infects and other animals, it was not for want of more: but, because the one mentioned in the text, is that which diftinguithes them moft remarkably from vegetables in general. The analogies, however, which fubfift between infects and other animals, are very numerous, and in order to mention fome of them, I fhall obferve, first, that both of them grow, and are propagated, almost entirely in the fame way. 3. That the internal parts of the one, are analogous to thofe of the others. All infects, like the larger animals, with few exceptions if any, have a stomach, intestines, a heart, veins, lungs, a brain, fpinal marrow, muscles, an ova→ ry, &c. 3. That infects likewife are endowed with fenfes. Áll have tafte and feeling, the greater part have fight, and probably alfo fmell, nor can it be doubted, that many have hearing. [The ears of infects have been lately demonftrated by Profeffor Fabricius, who published an account, with fi gures of thofe organs, in the crab and lobster, in the New Copenhagen Tranfactions, Vol. II. p. 375. That eminent entomologist found the external orifice of the organ in these animals, to be placed between the long and the short antennæ, the cochlea, &c. being lodged in the upper part of what Linnæus calls the thorax, near the base of the ferrated projection at its apex. As thefe animals, therefore, are true infects, it is reasonable to conclude, that the rest of the class are likewise provided with fimilar organs, in the fame places.] 4. That they appear alfo, to be endowed with the paffions, especially with that of love, fear and anger. 5. That they exhibit traces of memory, and a certain degree of intelligence. 6. That each has its peculiar industry, artifice, manner of attack, defence, and method of attending to its own prefervation. 7. That a diverfity of characters is obfervable among them. Some are bold, timid, active, flothful, patient, headlong, ftrong, weak, focial, folitary, neat, fluttish, temperate, voracious. In a word, hardly any thing is to be feen in the organs, difpofitions, manner of living, and acting in the larger animals, of which we may not find traces in infects; fo that it cannot be denied, but that their analogies with thefe animals, are incomparably more real, and more diftinct, than thofe with plants.

PACE 39, 1. 18.

Approach to the nature of vegetables. Although among in

Pp z

fects,