48 M1M1CEY, AND CTREE PEOTECTIVE 



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 phenomena, 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 



