36 CONTROLLED NATURAL SELECTION 



may be again sub-divided as in the following 

 table : 



The colour of an animal can, however, never 

 be considered as a unit. Some of the coloured 

 parts will be used for one purpose, others for 

 another. For instance, in many animals and 

 especially in birds, parts are conspicuously 

 coloured which are usually concealed, and 

 which are only displayed on definite occa- 

 sions and for definite purposes : thus, too, the 

 Red Admiral butterfly can, at will, display 



