Characters as Adaptive and Specific. 187 



their true plumage after a few generations. An excellent 

 observer (Mr. Hewitt) . . . found that he could not breed wild 

 ducks true for more than five or six generations, as they proved 

 so much less beautiful. The white collar round the neck of the 

 mallard became broader and more irregular, and white feathers 

 appeared in the duckling's wings &C. 1 " 



Now, such cases to which numberless others might 

 be added prove that even the subtle and incon- 

 spicuous causes incidental to domestication are 

 capable of inducing changes of specific character 

 quite as great, and quite as "stable," as any that 

 in a state of nature are taken to constitute specific 

 distinctions. Yet there can here be no suggestion 

 of utility, inasmuch as the change takes place in the 

 course of a few generations, and therefore without 

 leaving time for natural selection to come into play 

 even if it ever could come into play among the 

 sundry domesticated birds in question. 



But the facts of domestication also make for the 

 same conclusion in another way namely, by proving 

 that when time enough has been allowed for the pro- 

 duction of useless changes of greater magnitude, 

 such changes are not infrequently produced. And 

 the value of this line of evidence is that, great as are 

 the changes, it is impossible that either natural or 

 artificial selection can have been concerned in their 

 production. It will be sufficient to give two examples 

 both with regard to structure. 



The first I will render in the words whereby it 

 has already been stated in my own paper on 

 Physiological Selection, because I should like to take 

 this opportunity of answering Mr. Wallace's objection 

 to it. 



1 Var. vol. ii. p. 250. 



