REPRODUCTION is usually under stood to mean the restoration of a thing before existing and since destroyed. It is very well known that trees and plants may he raised from slips and cuttings ; and some late observations have shown, that there are some animals which have the same property. The polype (See IlvonA) was the first instance we had of this kind ; but we had scarcely time to wonder at the discovery M. Trembley had made, when M. Bonett discovered the same property in a species of water worm. Amongst the plants which may be raised from cuttings, there are some which seem to possess this quality in so eminent a degree, that the smallest por tion of them will become a complete tree again. A twig of willow, poplar, or many other trees, being planted in the earth, takes root, and becomes a tree, every piece of which will in the same manner produce other trees. The case is the same with these worms ; they are cut to pieces, and these several pieces become perfect animals ; and each of these may be again cut into a number of pieces, each of which will in the same manner produce an animal. It has been suppos ed by some that these worms were ovi parous ; but M. Bonett, on cutting one of them to pieces, having observed a slender substance, resembling a small filament, to move at the end of one of the pieces, separated it ; and on examin ing it with glases, found it to be a perfect worm, of the same form with its parent, which lived and grew larger in a vessel of water, into which he put it. These Small bodies are easily divided, and very readily complete themselves again, a day usually serving for the production of a head to the part that wants one ; and, in general, the smaller and more slender the worms are, the sooner they com plete themselves after this operation. When the bodies of the large worms are examined by the microscope, it is very easy to see the appearance of the young .worms alive, and moving about within them ; but it requires great precision and exactness to be certain of this; since the ramifications of the great artery have very much the appearance of young worms, and they are kept in a sort of continual motion by the systoles and diastoles of the several portions of the artery, which serve as so many hearts. It is very cer. tain, that what we force in regard to these animals, by our operations, is done also naturally every day in the brooks and ditches where they live. A curious observer will find in these places many of them without heads or tails, and solve without either ; as also other fragments of various kinds, all which are then in the act of completing themselves; but whether accidents have reduced them to this state, or they thus purposely throw off parts of their own body for the repro duction of more animals, it is not easy to determine. They are plainly liable to
many accidents, by which they lose the several parts of their body, and must pe rish very early if they had not a power of reproducing what was lost ; they often are broken into two pieces, by the resist ance of some hard piece of mud which they enter ; and they are subject to a dis ease, a kind of gangrene, rotting off the several parts of their bodies, and must inevitably perish by it, had they not this surprising property.
The reproduction of several parts of lobsters, crabs, &c. is one of the greatest curiosities in natural history. It seems, indeed, inconsistent with the modern sys tem of generation, which supposes the animal to be wholly formed in the egg, that, in lieu of an organical part of an ani mal cut off, another should arise perfect ly like it : the fact, however, is too well attested to be denied. The legs of lob sters, &c. consist each of five articula tions; now when any of the legs happen to break by any accident, as by walking, &c. which frequently happens, the frac ture is always found to be at the suture near the fourth articulation ; and what they thus lose is exactly reproduced in some time afterwards; that is, a part of the leg shoots out, consisting of four ar ticulations, the first whereof has two claws, as before ; so that the loss is en tirely repaired.
If the leg of a lobster be broken off by design at the fourth or fifth articulation, what is thus broke off is always repro duced. But if the fracture be made its the first, second, or third articulation, the reproduction is not so certain. And it is very surprising, that, if the fracture be made at these articulations, at the end of two or three days all the other articula tions are generally found broke off to the fourth, which, it is supposed, is done by the creature itself, to make the repro duction certain. The part reproduced is not only perfectly similar to that re trenched, but also, in a certain space of time, grows equal to it. Hence it is that we frequently see lobsters which have their two large legs unequal in all pro po And if the part reproduced be ken off, a second will succeed.