XI.] SPECIFIC GENESIS. 249 



ability the now variclics and forms, such as the memorable 

 one of the black-shouldered peacock. In all tliese 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' numerous in- 

 stances to show how excessively sensitive to various influ- 

 ences this system is. lie says: * " 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."' 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." " 



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 iu 

 the matter." " 



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

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



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

 "> Ibid., p. 26. " Ibid., p. 161. 



