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AFRICAN MIMETIC BUTTERFLIES 



still greater perfection. The model which makes such variation advantageous is not itself 

 immune, for though plentiful by reason of its comparative paucity of enemies, it yet has 

 its destroyers also, which keep within bounds what would otherwise be its ever-increasing 

 swarms. A species which has developed qualities which protect it from one form of enemy 

 may be exterminated by another pursuer which has itself developed special faculties for 

 effective pursuit. As has already been stated, we see only the present survivals, the forms 

 which are enjoying, perhaps only temporarily, the results of successful variation. 



Dr. Sharp's third objection, although it is actually aimed at the theory of mimicry, 

 applies equally well to the progressive stages in the evolution of any organ or structure in 

 animals or plants : it is, in fact, only an objection to mimicry in so far as it is an objection 

 to adaptive evolution of any kind. 



The fourth objection merits but little consideration. One of the most noticeable features 

 of the mimetic developments already illustrated is the manner in which the mimetic species 

 have departed from the normal pattern and coloration of their own genera, in order to resemble 

 the forms which serve as their models. To pursue this objection to its logical conclusion 

 would involve the assertion of the original creation of all the butterflies exactly as we now 

 see them, a suggestion which can hardly have been intended by the writer. We thus see 

 that three out of Dr. Sharp's four objections are criticisms of evolutionary theory in general, 

 and are not specially applicable to the theory of mimicry. 



We may now consider the basis on which the natural selection theory is founded. In 

 order adequately to support this view, there are two main contentions for which justification 

 must be found, namely, first, that some butterflies are less palatable to insect-eating enemies 

 than are others, and second, that butterflies are in fact preyed upon in the imago state by 

 birds and other insectivorous foes ; and further, that young birds do not instinctively know 

 what to eat and what to avoid. 



