網頁圖片
PDF
ePub 版

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

Page 176,1. 28.

Discharge a sensible smell. Many species of ichneumons ahd wood-bugs, have a very disagreeable smell. I have seen larvæ, not so large by half as a bean, and which are of the number of those that change into beetles, which send forth so strong a smell 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, smells so strongly of honey, that in the open air, 1 have sometimes smelt it, at the distance of thirty paces.

Page t77,1. 16.

This is a sort of web. We must not think, that, when we see stagnant waters, covered with a green and sibrou.3 pellicle, that this pellicle is always a web, woven by insects. It is generally a species of alga, which grows in still waters, and which is much relished by some small larvæ; perhaps, from their being so often found there, it has been thought, that they made it. At least, I have never found any such pellicle, which could be truly considered as the fabrication of any animal.

Page 177,1. last.

The appearance proceeds from certain species of butterflies—It is very common with Hies, and with all sorts ot moths and butterflies, after having disengaged ,themselves from their covering, while in the nymph or chrysalis state, and when their wings are unsolded and grown sirm, at the moment when they are disposing themselves to take their sirst flight, to discharge from the extremity of their abdomen, a quantity of superabundant humours, the secretion os which had been made, while they were in the nymph or chrysalis state. These humours have no resemblance to the natural excrements of those insects; they are of difserent colours,and those which fall from butterflies are often red. Such, for instance, are those of the small thorny caterpillars, which live in society on the nettle. These, and some others, when th?y are to undergo their changes, kave the plant on which they have seJ, and suspend themselves upon walls, when there are any at hand, and fr-jm this it has happened, rbat those red spots have been generally sound on waits} and were formerly most erroneously considered to be drops from a shower of blood.

Page 179,1. 8.

Tie targe reddijb yellow spiders. In general, spiders do not live in concord, except when very young. When they are larger, there is no longer any society or union among them, except at the time of coupling. Except at this time, if they are shut up together, they do not spare their own species, but kill one another without mercy: even those which do not eat one another, do so, one would think, out of pure ilUnature.

Page 179, \. penult.

Entirely deprived of every fart 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 5 but the species are rare, as I have hitherto only met with two kinds.

Page 180, L 9.

It if said, that some infe&s have an avers on. In Natural History, it is dangerous to admit marvellous facts on mere hear-say; 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 person, for instance, little versed in the art of making observations, should maintain, that the Jiead, 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 assured himself of the truth of the facts; I am entitled to doubt his assertion, 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 ihould drive away flies, while the flesh of other animals, and according to all appearance, that of the wolf itself, attracts them: we can still less conceive, how a cricket, whose bite is very gentle, and which seems not very capable of high flight, could contrive to kill so large a bird as the cuckoo, whose flight is very rapid, and which continually perches on trqes. But ,if, on the other hand, an author of

credit credit and intelligence, relates to me an extraordinary fact; for instance, that when a crab has lost a limb, another is produced in its place, and informs me, that in order to ascertain the fact, he has (hut up, and fed a number of mutilated crabs; that he has examined them with care, and details to me every step in the progress of the growth which these mutilated limbs made, from time to time, till they acquired the intire form and size of the one ^ost, I ought not to hesitate in believing, on his authority, such a fact, however wonderful and strange it may appear to me; because his integrity persuades me, that he is incapable of willingly imposing on me, and because all the accounts he gives me of his experiments, shew 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 test of experiment, that is, the antipathy between the toad and the spider- It is believed, almost every where, that when a toad passes 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 lost, if it bites him, he is instantly poisoned, and runs, with all expedition, to eat of a certain herb, which serves as a counter-poison; after which, he returns to the combat, which is accordingly renewed; but that, if he cannot find any of bis herb, he immediately swells and bursts in a few seconds. An opinion, so generally received, deserves to be examined; and accordingly, I have often attempted to make the experiment, by obliging a large spider to descend on a toad, or by putting a toad under a spider's web; but none of my attempts have ever succeeded, and none of my animals ever shewed the smallest disposition to a battle. Perhaps the experiment might succeed, if they were inclosed in a glass together: this still remains to be tried: in the mean time, it becomes those only, who have seen the fact, to affirm it as a truth.

Page 180,'L 15.

Some bisefts are subjefl to the Jlont. Of all the infects subject to this disorder, there are none of them whose disease is so uleful to us, as those oysters which produce pearls. M. de Reaumur believes, that they are formed in the body of the oyster, by the rupture of those vessels which contain the fluids that serve for the formation of the fhejl. These fluids, when extravasated, grow hard, a new fluid succeeds, and, fixing itself around the pearl already begun, it makes a second stratum; that stratum is followed by a third, and thus, the pearl is formed of several concentric strata. What confirms the opinion of this illustrious author, with regard to the formation of pearl?, is this; he found that the shell of the Pinna marina is composed of two different substances, the one of jhe colour of mother of pearl, and the other reddisti; and, that the parts of the animal containing - pearls, had a reddish or dark colour, according as the part affected corresponded with the dark or reddish part of the shell.—See Mem. de l'Acad. des Scien. 1717.

Page 183,1. 6.

Sometimes Jive and forty thousand animalcula. Some art must have been used to collect together so many animals, in so small a space, either by evaporating or filtrating the water, or in some other way; for it is not probable, that a single drop of water, so small as the size of a millet feed, should naturally contain so many thousands of animated be* ings. But what will appear still more difficult of belief to many people, is, that it was possible to make a calculation ne^r the truth, of so 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 discerned? The best microscopes in such a case.do not enable us to distinguish so small an animal, from any other corpuscle which swims in the (ame fluid. But, if they were alive, how could they be counted, even in the loosest way, considering, that then they must be swarming and struggling for room in so strait a place? The difficulty appears great; but it may be iolred, and it may be shown, that there is no impossibility in making a gross calculation. It may be done, for instance, in the following way: I would at first begin, by comparing the diameter of one of those small animals, considering it as spherical, to the axis of a sphere, of the size of a millet seed, and I would see 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 smaller than the sphere I compared it to; then, taking a drop of water, of the size of that sphere, and which swarms with animal?, the number of which I wisli to ascertain, I would allow it to dry up on the microscope, tMl -these animals were confounded in a single mass; I would .then, of that mass, form in my own mind, a spherical volume, and by comparing, however loosely, this volume, with, that of a millet feed, I would know the proportion in size, which these two spherical masses 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 observations, and in which it is difficult to determine things with precision, 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 sufficient for common purposes.

Page 185,1. a.

Red, like policed aepper. There are found in this country, flies of this kind, proceeding from a white maggot, with a head of a changeable shape, which spins a ci^ue, so thin, so close, and so transparent, that one would take it for a single membrane. It is impossible 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 never found any infect which came near it, except a certain beetle, proceeding from a white larva with six 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 respects, the lustre of both is so 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 stigmata only are white; but, it is a whiteness which resembles milk more than the diamond. However, h is certain, that, notwithstanding t]ie general disposition to consider all caterpillars as ugly and disgusting animate, there is not, except butterflies, any other kind of insect, and perhaps even any other animal, which affords so many instances of all the beautifi 1 colours. Gold, silver, and mother of pearl, are the only ones wanting: nor can we fay positively, that gold is wanting, for I know a caterpillar, which has, on the upper side of each articulation, four small yellowish spots, placed in a square form, which acquire the colour and splendor of gold,

« 上一頁繼續 »