400 RUDIMENTARY, ATROPHIED, [Cha*. XIV. 



organs are imperfect and useless. In works on natural history, 

 rudimentary organs are generally said to have been created " for 

 the sake jf symmetry," or in order " to complete the scheme of 

 nature." But this is not an explanation, merely a re-statement of 

 the fact. Nor is it consistent with itself: thus the boa-constrictor 

 has rudiments of hind-limbs and of a pelvis, and if it be said that 

 these bones have been retained " to complete the scheme of nature," 

 why, as Professor Weismann asks, have they not been retained by 

 other snakes, which do not possess even a vestige of these same 

 bones ? "What would be thought of an astronomer who maintained 

 that the satellites revolve in elliptic courses round thek planets 

 "for the sake of symmetry ,' - because the planets thus revolve 

 round the sun ? An eminent physiologist accounts for the presence 

 of rudimentary organs, by supposing that they serve to excrete 

 matter in excess, or matter injurious to the system ; but can we 

 suppose that the minute papilla, which often represents the pistil in 

 male flowers, aud which is formed of mere cellular tissue, can thus 

 ■act? Can we suppose that rudimentary teeth, which are subse- 

 quently absorbed, are beneficial to the rapidly growing embryonic 

 calf by removing matter so precious as phosphate of lime ? When 

 a man's fingers have been amputated, imperfect nails have been 

 known to appear on the stumps, and I could as soon believe that 

 these vestiges of nails are developed in order to excrete horny 

 matter, as that the rudimentary nails on the fin of the manatee 

 have been developed for this same purpose. 



On the view of descent with modification, the origin of rudimen- 

 tary organs is comparatively simple ; and we can understand to a 

 large extent the laws governing their imperfect development. We 

 have plenty of cases of rudimentary organs in our domestic pro- 

 ductions, — 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 hornless 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 



