138 MIMICRY AND VARIATION [ch. x 



butterflies possessing it at an advantage as compared 

 with the rest^. 



It is, nevertheless, possible that mimicry may have 

 played some part in connection with establishing the 

 new colour pattern in some of these South American 

 species. For if the new pattern had become estab- 

 lished in the predominant distasteful species, and if 

 some of the members of a palatable form {e.g. Proto- 

 gonius) were to shew a variation similar to that already 

 estabhshed in the distasteful species, and if further 

 there be granted the existence of appropriate enemies, 

 then it would be almost certain that the newer form in 

 palatable species would eventually replace the older 

 form. In such a case the part played by natural 

 selection would be the preservation of a chance sport 

 which happened to look like an unpalatable form. 

 There is no reason for regarding the change as neces- 

 sarily brought about by the gradual accumulation of 

 a long series of very small variations through the 

 operation of natural selection. 



^ In this connection it is of interest that a recent observer with 

 considerable breeding experience finds that the dark doubledayaria 

 variety of the Peppered Moth is more hardy than the typical form 

 (cf. p. 101). The swift success of the dark variety led some to regard 

 it as better protected against bird enemies. It is, however, not unlikely 

 that the deeper pigmentation is associated with some physiological 

 difference wliich makes for greater hardiness. See Bowater, Journal 

 of Genetics, vol. 3, 1914. 



