the act whereby a thing is produced anew, or grows a second time.
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 system of generation, which supposes the animal to be wholly formed in the egg; that, in lieu of an organic part of an animal cut off, another should arise perfectly like it: the fact, however, is too well attested to be denied.
The legs of lobsters, &c., consist each of five articulations: now when any of the legs happen to break, by any accident, as by walking, &c., which frequently happens, the fracture is always found to be at the fixture 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 articulations, the first whereof has two claws, as before; so that the loss is entirely repaired.
If the leg of a lobster be broken off by design at the fourth or fifth articulation, what is thus broken off is always reproduced. But, if the fracture be made in 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 articulations are generally found broken off to the fourth, which, it is supposed, is done by the creature itself, to make the reproduction certain. The part reproduced is not only similar to that retrenched, 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 proportions; and, if the part reproduced be broken off, a second will succeed.
In an essay on the reproduction of animals by the Abbé Spalanzani, that gentleman has asserted, that snails are endowed with a very extraordinary reproductive power; insomuch, that even when their heads are cut off, new ones are soon produced: but this has been found to be a mistake, and all the snails whose heads were cut off died sooner or later, though some lived a whole year after the operation. The Abbé's mistake was occasioned by his having only cut off part of the heads; by reason of the creatures contracting their bodies in order to avoid the injury. So far from being endowed with any power of reproducing their heads, these creatures are not even endowed with a power of reproducing their horns, or any part of them, when cut off.