xi] CONCLUSION 143 



they live. They are so distinct in colour that it is 

 difficult on this hypothesis to suppose that they are 

 all on the same footing in respect to their environment. 

 Yet if one is better off than the others, how is it that 

 these still exist? 



Those who have examined long series of these 

 cases of resemblance among butterflies find it hard to 

 believe that there is not some connection between 

 them apart from climatic influence. One feels that 

 they are too numerous and too striking to be all ex- 

 plained away as mere coincidences engendered by like 

 conditions. Nor is it improbable that natural selection 

 in the form of the discriminating enemy may have 

 played a part in connection with them, though a 

 different one from that advocated on the current theory 

 of mimicry. If we assume that sudden and readily 

 appreciable variations of the nature of "sports" turn 

 up from time to time, and if these variations happen to 

 resemble a form protected by distastefulness so closely 

 that the two can be confused by an enemy which has 

 learned to avoid the latter, then there would appear 

 to be good grounds for the mimicking sport becoming 

 established as the type form of the species. For it 

 has already been seen that a rare sport is not swamped 

 by intercrossing with the normal form, but that on the 

 contrary if it possess even a slight advantage, it must 

 rapidly displace the form from which it sprang (cf. 

 Chap. VIII). On this view natural selection in the form 

 of the discriminating enemy will have played its part, 

 but now with a difference. Instead of building up a 



