92 THE CASE OF PAPILIO P0LYTE8 [ch. vn 



forms of sweet pea and primula there is every reason 

 to suppose that they arose in the same way, that is to 

 say, as sudden sports or mutations and not by the 

 gradual accumulation of slight differences. 



But if we take this view, which is certainly most 

 consonant with the evidence before us, we must assign 

 to natural selection a different role from that which is 

 generally ascribed to it. We cannot suppose that 

 natural selection has played any part in the formation 

 of a mimetic likeness. The lil^eness turned up suddenly 

 as a sport quite independently of natural selection. 

 But although natural selection may have had nothing 

 to do with its production, it may nevertheless have 

 come into play in connection with the conservation of 

 the new form. If the new form possesses some advan- 

 tage over the pre-existing one from which it sprang, 

 is it not conceivable that natural selection will come 

 into operation to render it the predominant form? 

 To this question we shall try to find an answer in 

 the next chapter. 



