5 



58 Evohition and Adaptation 



degrees, and through selection, we meet with all the objec- 

 tions that have been urged, in general, against the theory of 

 natural selection. But if we assume here also that muta- 

 tions have occurred without relation to the environment, and, 

 having once appeared, determined in some cases the distribu- 

 tion of the species, we have at least a simple hypothesis that 

 appears to explain the facts. If it be claimed that the re- 

 semblance is, in some cases, too close for us to suppose that 

 it has arisen independently of the environment, it may be 

 pointed out that it has not been shown that such a close 

 resemblance is at all necessary for the continued existence 

 of the species, and hence the argument is likely to prove 

 too much. For instance, the most remarkable case of re- 

 semblance is that of Kallima, but in the light of a recent 

 statement by Dean it may be seriously asked whether there 

 is absolute need of such a close resemblance to a leaf. Even 

 if it be admitted that to a certain extent the butterfly is at 

 times protected by its resemblance to a leaf, it is not improb- 

 able that it could exist almost equally well without such a 

 close resemblance. If this is true, natural selection could 

 never have brought about such a close imitation of a leaf. 

 Cases like these of over-adaptation are not unaccountable on 

 the theory of mutation, for on this view the adaptation may 

 be far ahead of what the actual requirements for protection 

 demand. We meet occasionally, I think, throughout the liv- 

 ing world with resemblances that can have no such inter- 

 pretation, and a number of the kinds of adaptations to be 

 described in this chapter show the same relation. 



Some of the cases of mimicry appear also to fall under this 

 head ; although I do not doubt that many so-called cases of 

 mimicry are purely imaginary, in the sense that the resem- 

 blance has not been acquired on account of its relation to 

 the animal imitated. There is no need to question that in 

 some cases animals may be protected by their resemblance to 

 other animals, but it does not follow, despite the vigorous 



