Seite - 494 - in The Origin of Species

494 ORIGIN OF SPECIES metry," because the planets thus revolve round the sun? An eminent physiologist accounts for the presence of rudimen- tary organs, by supposing that they serve to excrete matter in excess, or matter injurious to the system; but can we sup- pose that the minute papilla, which often represents the pistil in male flowers, and which is formed of mere cellular tissue, can thus act? Can we suppose that rudimentary teeth, which are subsequently absorbed, are beneficial to the rapidly grow- ing embryonic calf by removing matter so precious as phos- phate of lime? When a man's fingers have been amputated, imperfect nails have been known to appear on the stumps, and T could as soon believe that these vestiges of nails are developed in order to excrete horny matter, as that the rudi- mentary nails on the fin of the manatee have been developed for this same purpose. On the view of descent with modification, the origin of rudimentary organs is comparatively simple; and we can understand to a large extent the laws governing their imper- fect development. We have plenty of cases of rudimentary organs in our domestic productions,—as the stump of a tail in tailless breeds,—the vestige of an ear in earless breeds of sheep,—the reappearance of minute dangling horns in horn- less breeds of cattle, more especially, according to Youatt, in young animals,—and the state of the whole flower in the cauliflower. We often see rudiments of various parts in monsters; but I doubt whether any of these cases throw light on the origin of rudimentary organs in a state of nature, further than by showing that rudiments can be produced ; for the balance of evidence clearly indicates that species under nature do not undergo great and abrupt changes. But we learn from the study of our domestic productions that the disuse of parts leads to their reduced size ; and that the result is inherited. It appears probable that disuse has been the main agent in rendering organs rudimentary. It would at first lead by slow steps to the more and more complete reduction of a part, until at last it became rudimentary,—as in the case of the eyes of animals inhabiting dark caverns, and of the wings of birds inhabiting oceanic islands, which have seldom been forced by beasts of prey to take flight, and have ultimately