96 Darwin, and after Darwin. 



the inherited effects of use and disuse was derived 

 from his careful measurements of the increase or 

 decrease which certain bones of our domesticated 

 animals have undergone, as compared with the cor- 

 responding bones of ancestral stocks in a state of 

 nature. He chose domesticated animals for these 

 investigations, because, while yielding unquestionable 

 cases of increased or diminished use of certain organs 

 over a large number of sequent generations, the results 

 were not complicated by the possible interference 

 of natural selection on the one hand, or by that 

 of the economy of nutrition on the other. For " with 

 highly-fed domesticated animals there seems to be 

 no economy of growth, or any tendency to the elimi- 

 nation of superfluous details^;'" seeing that, among 

 other considerations pointing in the same direction, 

 " structures which are rudimentary in the parent 

 species, sometimes become partially re-developed in 

 our domesticated productions^." 



The method of Darwin's researches in this con- 

 nexion was as follows. Taking, for example, the case 

 of ducks, he carefully weighed and measured the 

 wing-bones and leg-bones of wild and tame ducks; 

 and he found that the wing-bones were smaller, 

 while the leg-bones were larger, in the tame than in 

 the wild specimens. These facts he attributed to many 

 generations of tame ducks using their wings less, and 

 their legs more, than was the case with their wild 

 ancestry. Similarly he compared the leg-bones of 

 wild rabbits with those of tame ones, and so forth — 

 in all cases finding that where domestication had led 

 to increased use of a part, that part was larger than in 

 ' Variation of Plants and Animals, vol. ii. p. 289. * Ibid. p. 346. 



