CHAPTER XI 



CONCLUSION 



From the facts recorded in the preceding chapters 

 it is clear that there are difficulties in the way of 

 accepting the mimicry theory as an explanation of the 

 remarkable resemblances which are often found between 

 butterflies belonging to distinct groups. Of these 

 difficulties two stand out beyond the rest, viz., the 

 difficulty of finding the agent that shall exercise the 

 appropriate powers of discrimination, and the difficulty 

 of fitting in the theoretical process involving the in- 

 cessant accumulation of minute variations with what 

 is at present known of the facts of heredity. 



With regard to the former of these two difficulties 

 we have seen that the supporters of the theory regard 

 birds as the main selective agent. At the outset we 

 are met with the fact that relatively few birds have been 

 observed to prey habitually on butterflies, while some 

 at any rate of those that do so shew no discrimination 

 between what should be theoretically pleasant to eat 

 and what should not be pleasant. Even if birds are 

 the postulated enemies it must be further shewn 

 that they exercise the postulated discrimination. It 

 is required of them that they should do two things. 



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