No. 506] DABWJX AXJ) MUTATIOX TIIEOHY 



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Even when treating of organisms in a state of nature, 

 however, he admits that "there will he a constant tend- 

 ency in natural selection to preserve the most divergent 

 offspring of any one species." 10 Eeturning to the sub- 

 ject of artificial selection, Mr. Darwin says: 



No man would ever try to make a fan-tail till he saw a pigeon with 



more likely it would be to catch his attention." 

 In another place he says : 



It is probable that some breeds, such as the semi-monstrous Niata 

 cattle, and some peculiarities, such as being hornless, &c. have ap- 

 peared suddenly owing to what we may call, in our ignorance, spon- 



has occasionally happened that deviations of sirurtuiv more strongly 

 pronounced than mere individual differences, yet by no means deserving 

 to be called monstrosities have been taken advantage of. 12 



Now, in his work on Animals and Plants under Do- 

 mestication Darwin has given a long list of these widely 

 varying forms from each of which has descended a new 

 race conforming to his own test of a species, namely its 

 possession of "the power of remaining for a good long 

 period constant . . . combined with an appreciable 

 amount of difference." 13 One of the most striking of 

 these cases is that of the "japanned" or "black-shoul- 

 dered" peacocks which have occasionally appeared ->ud 

 denly in flocks of the common kind," which "propagate 

 their kind quite truly," which, according to good au- 

 thority, "form a distinct and natural species," and which 

 tend "at all times and in many places to reappear." 14 

 Mr. Darwin rejects the idea that these birds are the re- 

 sult of hybridization and reversion and declares in favor 



