XI] CONCLUSION 153 



others, working as it were upon a plastic organism, 

 moulding it little by little to a more and more perfect 

 adaptation to its surroundings. On this view adapta- 

 tion is easy to understand. The simplicity of the 

 explanation is in itself attractive. But when the 

 facts come to be examined critically it is evident that 

 there are grave, if not insuperable, difficulties in the way 

 of its acceptance. To outline some of these has been 

 the object of the present essay. Though suggestions 

 have been made as to the lines along which an ex- 

 planation may eventually be sought it is not pre- 

 tended that the evidence is yet strong enough to 

 justify more than suggestions. Few cases of mimicry 

 have as yet been studied in any detail, and until this 

 has been done many of the points at issue must remain 

 undecided. Nevertheless, the facts, so far as we at 

 present know them, tell definitely against the views 

 generally held as to the part played by natural selection 

 in the process of evolution. 



