232 Evolution and Adaptation 



unable to find any statements of this sort in Lamarck's 

 writings. 



The following cases that Darwin tried to explain through 

 the inheritance of acquired characters are exactly like those 

 to which Lamarck applied his theory. The bones of the 

 wing of the domestic duck weigh less than those of the wild 

 duck, and the bones of the leg more. Darwin believes this 

 is due to the effects of the inheritance of acquired characters. 

 The drooping ears of many domestic mammals are also 

 explained by him as a result of disuse — "the animals being 

 seldom much alarmed." In speaking of the male of the 

 beetle, Onites apelles, Darwin quotes Kirby to the effect that 

 the tarsi are so habitually lost that the species has been 

 described without this part of the foot. In the sacred beetle 

 of Egypt the tarsus is totally absent. Hence he concludes 

 that the absence of tarsi in the sacred beetle, and the rudi- 

 mentary condition of the tarsus in others, is probably the 

 result of disuse, rather than a case of inheritance of a muti- 

 lation. Darwin grants that "the evidence that accidental 

 mutilations can be inherited is at present not decisive, but 

 the remarkable case observed by Brown-S^quard in guinea- 

 pigs of the inherited effects of operations should make us 

 cautious in denying this tendency." 



The wingless condition of several insects inhabiting oceanic 

 islands has come about, Darwin thinks, through disuse. The 

 ostrich also, owing to its increase in size, made less use of its 

 wings and more use of its legs, with the result that its wings 

 degenerated and its legs got stronger. The rudimentary 

 condition of the eyes of the mole is the result of disuse, 

 "aided perhaps by natural selection." Many of the ani- 

 mals inhabiting the caves of Kentucky and of Carniola 

 are blind, and this is ascribed to disuse. "As it is diffi- 

 cult to imagine that the eyes, though useless, could be in 

 any way injurious to animals living in darkness, their loss 

 may be attributed to disuse." The long neck of the giraffe 



