A Dilemma 



Kallima continues its way, specifically and ab- 

 surdly dead-leafwards, until to-day it is a much 

 too fragile thing to be otherwise than very 

 gingerly handled by its rather anxious foster- 

 parents, the Neo-Darwinian selectionists." It 

 is obvious that if natural selection has produced 

 so highly specialised an organism as the dead- 

 leaf butterfly, every minute variation must be of 

 value and have been seized upon by natural 

 selection. 



Thus the Wallaceians are on the horns of a 

 dilemma. If they assert, as they appear to do, 

 that every infinitesimal variation has a survival 

 value, they find it difficult to explain the exist- 

 ence, side by side of such forms as the hooded and 

 carrion crows, to say why in some species of bird 

 both sexes assume a conspicuous nuptial plumage 

 at the very time when they stand most in need 

 of protective coloration, why the cock paradise 

 flycatcher is chestnut for the first two years of 

 his life and then turns as white as snow. If, on 

 the other hand, the Wallaceians assert that small 

 variations are unimportant and have no survival 

 they are, as Kellog points out, in trouble over 

 the close and detailed resemblance which the 

 Kallima butterflies bear to dead leaves. 



10. An objection to the Darwinian theory which 

 has been advanced by Conn, Henslow, D. Dewar, 

 and others, is that the selection theory fails to 

 take into account the effects of chance. " If," 



47 



