XL] SPECIFIC GENESIS. 249 



ability the new varieties and forms, such as the memorable 

 one of the black-shouldered peacock. In all these cases we 

 do not have abortions or monstrosities, but more or less har- 

 monious forms, often of great functional activity, endowed 

 with marked viability and generative prepotency, except in 

 the case of hybrids, when we often find even a more marked 

 generative impotency. 



It seems probable therefore that new species may arise 

 from some constitutional affection of parental forms an 

 affection mainly, if not exclusively, of their generative sys- 

 tem. Mr. Darwin has carefully collected 7 numerous in- 

 stances to show how excessively sensitive to various influ- 

 ences this system is. He says : 8 " Sterility is independent 

 of general health, and is often accompanied by excess of 

 size, or great luxuriance," and, " No one can tell, till he tries, 

 whether any particular animal will breed under confinement, 

 or any exotic plant seed freely under culture." Again, 

 " When a new character arises, whatever its nature may be, 

 it generally tends to be inherited, at least in a temporary, 

 and sometimes in a most persistent manner." 8 Yet the 

 obscure action of conditions will alter characters long inher- 

 ited, as the grandchildren of Aylesbury ducks removed to a 

 distant part of England, completely lost their early habit of 

 incubation, and hatched their eggs at the same time with 

 the common ducks of the same place." 10 



Mr. Darwin quotes Mr. Bartlett as saying : " It is remark- 

 able that lions breed more freely in travelling collections 

 than in the zoological gardens ; probably the constant ex- 

 citement and irritation produced by moving from place to 

 place, or change of air, may have considerable influence in 

 the matter." " 



7 See especially " Animals and Plants under Domestication," vol. ii., 

 chap, xviii. 8 " Origin of Species," 5th edit., pp. 323, 324. 



9 " Animals and Plants under Domestication," vol. ii., p. 2. 



10 Ibid., p. 25. 1J Ibid., p. 151. 



