that the velocity of their agitations does not depend on any thing, perhaps, but the mere will of the animal.

PAGE 176, 1. 28.

Difcharge a fenfible fmell. Many fpecies of ichneumons and wood-bugs, have a very difagreeable fmell. I have feen larvæ, not fo large by half as a bean, and which are of the number of those that change into beetles, which fend forth fo strong a fmell of box-wood, that one could not remain in a room where there were only two or three of them. A kind of large cantharis in this country, fmells fo ftrongly of honey, that in the open air, I have fometimes fmelt it, at the diftance of thirty paces.

PAGE 177, 1. 16.

This is a fort of web. We must not think, that, when we fee ftagnant waters, covered with a green and fibrous pellicle, that this pellicle is always a web, woven by infects. It is generally a fpecies of alga, which grows in ftill waters, and which is much relifhed by fome fmall larvæ; perhaps, from their being fo often found there, it has been thought, that they made it. At least, I have never found any fuch pellicle, which could be truly confidered as the fabrication of any animal.

PAGE 177, 1. last.

The appearance proceeds from certain fpecies of butterflies. It is very common with flies, and with all forts of moths and butterflies, after having difengaged themselves from their covering, while in the nymph or chryfalis ftate, and when their wings are unfolded and grown firm, at the moment when they are difpofing themselves to take their first flight, to difcharge from the extremity of their abdomen, a quantity of fuperabundant humours, the fecretion of which had been made, while they were in the nymph or chryfalis ftate. These humours have no refemblance to the natural excrements of thofe infects; they are of different colours," and thofe which fall from butterflies are often red. Such, for inftance, are thofe of the final! thorny caterpillars, which live in fociety on the nettle. Thefe, and fome others, when they are to undergo their changes, leave the plant ou which they have fed, and fufpend themfelves upon walls, when there are any at hand, and from this it has happened,.

that

that thofe red fpots have been generally found on walls, and were formerly moft erroneously confidered to be drops from a fhower of blood.

PAGE 179, 1. 8.

The large reddifh yellow spiders. In general, fpiders do not live in concord, except when very young. When they are larger, there is no longer any fociety or union among them, except at the time of coupling. Except at this time, if they are fhut up together, they do not fpare their own fpecies, but kill one another without mercy: even those which do not eat one another, do fo, one would think, out of pure ill-nature.

PAGE 179, 1. penult.

Entirely deprived of every fort of food. I think I have al ready observed, that there are caterpillars, which, without being reduced to it by this extremity, eat one another from mere gluttony; but the fpecies are rare, as I have hitherto only met with two kinds.

PAGE 180, 1. 9.

It is faid, that fome infects have an averfion. In Natural Hiftory, it is dangerous to admit marvellous facts on mere hear-fay; but we must not, on the other hand, reject what is wonderful, because it appears to us improbable: we ought to examine Nature, and attend to the proofs on which the relation is made. If a perfon, for instance, little versed in the art of making obfervations, fhould maintain, that the head, and the tail of a wolf were good for keeping off flies, that crickets kill the cuckoo, and at the fame time, do not explain how he has acquired the knowledge, nor by what experiments he has affured himself of the truth of the facts; I am entitled to doubt his affertion, the more, as relations of this kind have the air of fables, and that it is with difficulty we can believe that the head and tail of a wolf fhould drive away flies, while the flesh of other animals, and according to all appearance, that of the wolf it felf, attracts them: we can ftill lefs conceive, how a cricket, whofe bite is very gentle, and which feems not very capable of high flight, could contrive to kill fo large a bird as the cuckoo, whofe flight is very rapid, and which continually perches on trees. But if, on the other hand, an author of

credit and intelligence, relates to me an extraordinary fact; for inftance, that when a crab has loft a limb, another is produced in its place, and informs me, that in order to af certain the fact, he has shut up, and fed a number of mutilated crabs; that he has examined them with care, and details to me every step in the progrefs of the growth which thefe mutilated limbs made, from time to time, till they acquired the intire form and fize of the one loft, I ought not to hesitate in believing, on his authority, fuch a fact, however wonderful and strange it may appear to me; because his integrity perfuades me, that he is incapable of willingly impofing on me, and because all the accounts he gives me of his experiments, fhew me, that he was not himself deceived.

Of the four examples of antipathy, mentioned by our author, there is only one which can easily be brought to the teft of experiment, that is, the antipathy between the toad and the fpider. It is believed, almost every where, that when a toad paffes under the web of a spider, this latter lets itself down, in order to bite the toad, which, on his part, expects it with open mouth; that, if he catches it, it is loft, if it bites him, he is inftantly poifoned, and runs, with all expedition, to eat of a certain herb, which ferves as a counter-poifon; after which, he returns to the combat, which is accordingly renewed; but that, if he cannot find any of his herb, he immediately fwells and burfts in a few feconds. An opinion, fo generally received, deferves to be examined; and accordingly, I have often attempted to make the experiment, by obliging a large fpider to defcend on a toad, or by putting a toad under a spider's web; but none of my attempts have ever fucceeded, and none of my animals ever fhewed the smalleft difpofition to a battle. Perhaps the experiment might fucceed, if they were inclosed in a glafs together this ftill remains to be tried: in the mean time, it becomes thofe only, who have seen the fact, to affirm it as a truth.

PAGE 180, 1. 15.

Some infects are fubject to the ftone. Of all the infects fubject to this diforder, there are none of them whose dif cafe is fo useful to us, as thofe oyfters which produce pearls. M. de Reaumur believes, that they are formed in the body of the oyster, by the rupture of thofe veffels which contain the fluids that ferve for the formation of the thell. Thefe

fluids, when extravafated, grow hard, a new fluid fucceeds, and, fixing itfelf around the pearl already begun, it makes a fecond ftratum; that ftratum is followed by a third, and thus, the pearl is formed of feveral concentric ftrata. What confirms the opinion of this illuftrious author, with regard to the formation of pearls, is this; he found that the shell of the Pinna marina is compofed of two different fubftances, the one of the colour of mother of pearl, and the other reddish; and, that the parts of the animal containing -pearls, had a reddith or dark colour, according as the part affected correfponded with the dark or reddish part of the fhell. See Mem. de l'Acad. des Scien. 1717.

PAGE 183, 1. 6.

Sometimes five and forty thousand animalcula. Some art must have been used to collect together fo many animals, in fo fmall a space, either by evaporating or filtrating the water, or in fome other way; for it is not probable, that a fingle drop of water, fo fmall as the fize of a millet feed, should naturally contain fo many thousands of animated be ings. But what will appear ftill more difficult of belief to many people, is, that it was poffible to make a calculation near the truth, of fo great a number of animals; for, they were either dead or living at the time they were counted. If they were dead, how could they be difcerned? The beft microscopes in such a case,do not enable us to distinguish fo fmall an animal, from any other corpufcle which fwims in the fame fluid. But, if they were alive, how could they be counted, even in the loofeft way, confidering, that then they must be fwarming and struggling for room in so ftrait a place? The difficulty appears great; but it may be folved, and it may be shown, that there is no impoffibility in making a grofs calculation. It may be done, for instance, in the following way: I would at firft begin, by comparing the diameter of one of thofe fmall animals, confidering it as fpherical, to the axis of a fphere, of the fize of a millet feed, and I would fee how much the one exceeds the other; now, as spheres are to one another, in the triplicate ratio of their axis, this would inform me at once, how many times the animal is fmailer than the fphere I compared it to; then, taking a drop of water, of the fize of that sphere, and which fwarms with animals, the number of which I wish to afcertain, I would allow it to dry up on the microfcope, till

thefe

thefe animals were confounded in a fingle mafs; I would then, of that mass, form in my own mind, a fpherical volume, and by comparing, however loofely, this volume, with that of a millet feed, I would know the proportion in fize, which these two spherical maffes bear to each other, which would lead me to ascertain the number of the animalcula which the drop I was examining contained. Such calculations, as they depend on very nice obfervations, and in which it is difficult to determine things with precifion, cannot be made with very great accuracy; but, if it is difficult to attain the perfect truth, we, however, would not be very far wrong, and this method is fufficient for common purposes.

PAGE 185, 1. 2.

Red, like polifhed copper. There are found in this country, flies of this kind, proceeding from a white maggot, with a head of a changeable fhape, which fpins a coque, fo thin, fo cofe, and fo tranfparent, that one would take it for a fingle membrane. It is impoffible to conceive more vivid, or more beautiful colours, than the golden and fiery colours which Sparkle on the body of the fly of this maggot. I have ne

ver found any infect which came near it, except a certain beetle, proceeding from a white larva with fix feet, and a brown head, which lives on the white nettle. The colour of this beetle, differs from that of the fly, only in this, that the gold prevails more in the beetle; in other refpects, the luftre of both is fo great, that I believe it perfectly inimitable by art.

PAGE 185, 1. last.

Some have the whiteness of the diamond. The tubercles on the caterpillar of the Phalæna caja, which the author cites in a note, as an example, are black. Its ftigmata only are white; but, it is a whitenefs which refembles milk more than the diamond. However, it is certain, that, notwithftanding the general difpofition to confider all caterpillars as ugly and difgufting animals, there is not, except butterflies, any other kind of infect, and perhaps even any other animal, which affords fo many inftances of all the beautif colours. Gold, filver, and mother of pearl, are the only ones. wanting: nor can we fay pofitively, that gold is wanting, for I know a caterpillar, which has, on the upper fide of each articulation, four fmall yellowith fpots, placed in a fquare form, which acquire the colour and splendor of gold,