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. 
to. 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 
