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 



