Until recently birds were regarded as possessing a very low degree of regenerative capacity, and, as a matter of fact, they cannot replace a leg or a wing wholly or in part; but, what is otherwise unheard of among higher vertebrates, they can renew the whole anterior portion of the skeleton of the face, the bill, and can indeed almost reconstruct it with new bones and horny parts. Von Kennel communicated a case of this kind in regard to a stork, and for a long time this remained an isolated case, but a few years ago Bordage showed that, in the cocks which are used in the Island of Bourbon for the favourite sport of cock-fighting, the bill is regularly renewed when it has been broken off or shattered. Quite recently Barfurth gave an account of a case of complete renewal of a broken bill in a parrot. Yet it should not astonish us that the bill in birds has such a high regenerative power, for of all parts in a bird it is the one that is most readily injured; with it the bird defends itself against its enemies and its rivals, masters its prey, and tears it to pieces, pecks holes in trees (woodpecker), or climbs (parrot), or digs and burrows in the ground, or builds its nest, and so on. That the faculty of regeneration could be developed to so high a degree in relation to this particular part of the body, while the rest of the very important but rarely injured parts do not possess it at all, again points to the conclusion that the faculty of regeneration has an adaptive character.