The evolution theory . he skeleton of the face,the bill, and can indeed almost reconstructit with new bones and horny parts. YonKennel communicated a case of this kind inregard to a stork, and for a long time thisremained an isolated case, but a few yearsago Bordage showed that, in the cocks whichare used in the Island of Bourbon for thefavourite sport of cock-fighting, the bill isregularly renewed when it has been brokenoff* or shattered. Quite recently Barfurth gave an account of a caseof complete renewal of a broken bill in a parrot. Yet it shouldnot astonish us that the bill in birds has s
The evolution theory . he skeleton of the face,the bill, and can indeed almost reconstructit with new bones and horny parts. YonKennel communicated a case of this kind inregard to a stork, and for a long time thisremained an isolated case, but a few yearsago Bordage showed that, in the cocks whichare used in the Island of Bourbon for thefavourite sport of cock-fighting, the bill isregularly renewed when it has been brokenoff* or shattered. Quite recently Barfurth gave an account of a caseof complete renewal of a broken bill in a parrot. Yet it shouldnot astonish us that the bill in birds has such a high regenera-tive power, for of all parts in a bird it is the one that is most readilynijured; with it the bird defends itself against its enemies and itsrivals, 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 regenera-tion could be developed to so high a degree in relation to this. Fig. 97. A, a Planarian,which has been divided intotwo by a longitudinal half can grow intoan entire animal. B, theleft half at the beginningof the regenerative , the same completed. AfterMorgan. EEGENERATION 15 particular part of the bocl}^, while the rest of the very importantbut rarely injured parts do not possess it at all, again points tothe conclusion that the faculty of regeneration has an adaptivecharacter. It does not affect matters to discover cases in which we cannotrecognize this relation between the regenerative capacity of a partand its importance or its liability to injury. Such instances do notlessen the convincingness of the positive cases, since we do not knowthe exact conditions which may lead to the increase of regenerativecapacit}^ in a part, and, above all, since we do not know^ the rate atwhich such an increase may take place. If adaptation in generaldepends upon processes of selection, these processes must also be ableto
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
