cox, DARWIN AND THE MUTATION THEORY 437 



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

 veloped in some slight degree in an unusual manner, or a pouter till he saw a pigeon 

 with a crop of somewhat unusual size; and the more abnormal or unusual any char- 

 acter was when it first appeared the 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 appeared suddenly owing to 

 what we may call, in our ignorance, spontaneous variation ; . . . . During the process 

 of methodical selection it has occasionally happened that deviations of structure 

 more strongly pronounced than mere individual differences, yet by no means de- 

 serving to be called monstrosities have been taken advantage of." ^ 



Now, in his work on "Animals and Plants Under Domestication", Dar- 

 win 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." ^ One of the 

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

 dered" peacocks which have occasionally appeared "suddenly in flocks of 

 the common kind," which "propagate their kind quite truly," which, ac- 

 cording to good authority, "form a distinct and natural species," and 

 which tend "at all times and in many places to reappear." * Mr. Darwin 

 rejects the idea that these birds are the result of hybridization and rever- 

 sion and declares in favor of their being "a variation induced by some 

 unknown cause," and says that "on this view the case is the most 

 remarkable one ever recorded of the abrupt appearance of a new form 

 which so closely resembles a true species that it has deceived one of the 

 most experienced of living ornithologists." In all points this case agrees 

 with the modern idea of a mutation, even in the respect that it comes from 

 a family of birds not usually considered very variable. 

 Concerning fowls, Mr. Darwin remarks : 



"Fanciers, whilst admitting and even overrating the effects of crossing the 

 various breeds, do not sufficiently regard the probability of the occasional birth, 

 during the course of centuries, of birds with abnormal and hereditary peculiarities. 

 .... Whenever, in the course of past centuries, a bird appeared with some slight ab- 

 normal structure, such as with a lark-like crest on its head, it would probably often 

 have been preserved from that love of novelty which leads some persons in England 

 to keep rumpless fowls and others in India to keep frizzled fowls. And after a 



» " Origin of Species," 6th ed., p. 28. 



2 " Animals and Plants Under Domestication," 2d ed., 1875, Vol. I, p. 96. See also, 

 Vol. II, pp. 189-90. 



3 " More Letters of Charles Darwin," 1903, Vol. I, p. 252. 



* " Animals and Plants Under Domestication," 2d ed., 1875, Vol. I, pp. 305-7. 



