I40 MENDELISM chap. 



was common and A. echeria was rare, its resemblance 

 to the more plentiful distasteful form would give it 

 the advantage over mima and allow it to establish 

 itself in place of the latter. On the modern Dar- 

 winian view natural selection gradually shapes mima 

 into the wahlbergi form owing to the presence of A. 

 dominicanus ; on the Mendelian view natural selec- 

 tion merely conserves the wahlbergi form when once 

 it has arisen. Now this case of mimicry is one 

 of especial interest, because we have experimental 

 evidence that the relation between mima and 

 wahlbergi is a simple Mendelian one, mima here 

 being the dominant and wahlbergi the recessive 

 form. The two have been proved to occur in 

 families bred from the same female without the 

 occurrence of any intermediates, and the fact that 

 the two segregate cleanly is strong evidence in 

 favour of the Mendelian view. On this view the 

 genera Amauris and Euralia contain a similar set 

 of pattern factors, and the conditions, whatever they 

 may be, which bring about mutation in the former 

 lead to the production of a similar mutation in the 

 latter. Of the different forms of Euralia produced 

 in any region that one has the best chance of 

 survival, through the operation of natural selection, 

 which resembles the most plentiful Amauris form. 

 Mimetic resemblance is a true phenomenon, but 

 natural selection plays the part of a conservative, 

 not of a formative agent. 



It is interesting to recall that in earlier years 

 Darwin was inclined to ascribe more importance to 

 " sports " as opposed to continuous minute variation, 

 and to consider that they might play a not incon- 



