fharpened at the point, pierces the substance which contains the food, and then opens within the wound, to allow the inclofed tube, through which the juice is extracted, to perform its office. Can any mechanifm be plainer than this is; or furpass this?

V. The metamorphosis of infects from grubs into moths and flies, is an astonishing procefs. A hairy caterpillar is transformed into a butterfly. Obferve the change. We have four beautiful wings, where there were none before; a tubular probofcis, in the place of a mouth with jaws and teeth: fix long legs, inftead of fourteen feet. In another cafe, we fee a white, fmooth, foft worm. turned into a black, hard, cruftaceous beetle, with gauze wings. Thefe, as I faid, are astonishing proceffes, and muft require, as it fhould seem, a proportionably artificial apparatus. The hypothefis which appears to me most probable is, that, in the grub, there exift at the fame time three animals, one within another, all nourished by the fame digeftion, and by a communicating circulation; but in different stages of maturity. The latest difcoveries, made by naturalifts, feem to favour this fuppofition. The infect already equipped

with wings, is defcried under the membranes both of the worm and nymph. In fome fpecies, the probofcis, the antennæ, the limbs and wings of the fly, have been obferved to be folded up within the body of the caterpillar; and with fuch nicety, as to occupy a small fpace only under the two firft wings. This being fo, the outermoft animal, which befide its own proper character ferves as an integument to the other two, being the furthest advanced, dies, as we fuppofe, and drops off first. The fecond, the pupa or chryfalis, then offers itself to obfervation. This alfo, in its turn, dies; its dead and brittle hufk falls to pieces, and makes way for the appearance of the fly or moth. Now, if this be the case, or indeed whatever explication be adopted, we have a profpective contrivance of the most curious kind: we have organizations three deep, yet a vascular system, which fupplies nutrition, growth, and life, to all of them together.

VI. Almost all infects are oviparous. Nature keeps her butterflies, moths and caterpillars, locked up during the winter in their egg ftate; and we have to admire the various devices, to which, if we may fo speak, the fame nature hath reforted, for the fecurity of

the egg. Many infects inclose their eggs in a filken web; others cover them with a coat of hair, torn from their own bodies; fome glue them together; and others, like the moth of the filkworm, glue them to the leaves upon which they are depofited, that they may not be shaken off by the wind, or washed away by rain: fome again make incifions into leaves, and hide an egg in each incifion; whilst fome envelope their eggs with a foft fubftance, which forms the firft aliment of the young animal; and fome again make a hole in the earth, and, having ftored it with a quantity of proper food, depofit their egg in it. In all which we are to obferve, that the expedient depends, not fo much upon the addrefs of the animal, as upon the physical refources of his conftitution.

The art alfo with which the young infect is coiled up in the egg, prefents, where it can be examined, a fubject of great curiofity. The infect, furnished with all the members which it ought to have, is rolled up into a form which seems to contract it into the leaft poffible space; by which contraction, notwithstanding the fmallness of the egg, it has room enough in its apartment and to spare. This folding

of

of the limbs appears to me to indicate a special direction; for, if it were merely the effect of compreffion, the collocation of the parts would be more various than it is. In the same species, I believe, it is always the fame.

These observations belong to the whole infect tribe, or to a great part of them. Other obfervations are limited to fewer fpecies; but not, perhaps, less important or fatisfactory.

I. The organization in the abdomen of the filkworm or Spider, whereby thefe infects form their thread, is as inconteftably mechanical, as a wire-drawer's mill. In the body of the filkworm are two bags, remarkable for their form, pofition, and ufe. They wind round the inteftine; when drawn out they are ten inches in length, though the animal itself be only two. Within thefe bags, is collected a glue; and communicating with the bags, are two paps or outlets, perforated, like a grater, by a number of fmall holes. The glue or gum, being paffed through these minute apertures, forms hairs of almost imperceptible fineness; and thefe hairs, when joined, compofe the filk which we wind off from the cone, in which the filkworm has wrapped itself up; in the fpider the web is 2A 3 formed

formed of this thread. In both cafes, the extremity of the thread, by means of its adhefive quality, is first attached by the animal to fome external hold; and the end being now faftened to a point, the infect, by turning round its body, or by receding from that point, draws out the thread through the holes above defcribed, by an operation, as hath been obferved, exactly fimilar to the drawing of wire. The thread, like the wire, is formed by the hole through which it paffes. In one respect there is a difference. The wire is the metal unaltered, except in figure. In the animal process, the nature of the substance is fomewhat changed, as well as the form: for, as it exifts within the infect, it is a foft, clammy, gum or glue. The thread acquires, it is probable, its firmness and tenacity from the action of the air upon its furface, in the moment of expofure; and a thread so fine is almost all furface. This property, however, of the pafte, is part of the contrivance.

The mechanifm itself confifts of the bags, or refervoirs, into which the glue is collected, and of the external holes communicating with these bags: and the action of the machine is feen, in the forming of a thread, as wire is formed, by forcing the material already prepared, through

holes