48 MIMICRY, AND OTHER PROTECTIVE 
to their conditions of life has long been recognised, 
and has been imputed either to an originally created 
specific peculiarity, or to the direct action of climate, 
soil, or food. Where the former explanation has been 
accepted, it has completely checked inquiry, since we 
could never get. any further than the fact of the 
adaptation. There was nothing more to be known 
about the matter. The second explanation was soon 
found to be quite inadequate to deal with all. the varied 
phases of the phznomena, and to be contradicted ‘by 
many well-known facts. For example, wild rabbits are 
always of grey or brown tints well suited for conceal- 
ment among grass and fern. But when these rabbits 
are domesticated, without any change of climate or 
food, they vary into white or black, and these varie- 
ties may be multiplied to any extent, forming white 
or black races. Exactly the same thing has occurred 
with pigeons; and in the case of rats and mice, 
the white variety has not been shown to be at all 
dependent on alteration of climate, food, or other 
external conditions. In many cases the wings of an 
insect not only assume the exact tint of the bark | 
or leaf’ it is accustomed to rest on, but the form 
and veining of the leaf or the exact rugosity of 
the bark is imitated ; and these detailed modifications 
cannot be reasonably imputed to climate or to food, 
since in many cases the species does not feed on 
the substance it resembles, and when it does, no 
reasonable connexion can be shown to exist between 
the supposed cause and the effect produced. It was 
