122 THE DARWINIAN THEORY 



illustrating the preservation and accentuation of 

 colour through the agency of Natural Selection — 

 one of the most striking of the later developments 

 of the theory. 



Significant Colours. 



These are colours which are of direct advantage 

 to their possessor as colour, and not merely because 

 they are associated with other properties which are 

 useful, as in the case of haemoglobin and chlorophyll. 

 The classification of these colours is a matter of some 

 difficulty, for cross-relations occur which are difficult 

 to express. 



There are three chief classes or groups : — 

 i. Apatetic ; the purpose of which, or rather the 

 object gained by which, is to hinder recognition by 

 other animals. 



2. Sematic, or signalling colours ; the purpose of 

 which is to facilitate or aid recognition by animals of 

 the same or of other kinds. 



3. Epigamic ; which include those cases in which 

 differences occur between the male and female sex, 

 as in the peacock and pea-hen, the duck and drake, 

 &c. This is a special and important group. 



Apatetic Colours are again divided into : 



a. Protective resemblances, aiding escape from 



enemies, as in those cases where animals re- 

 semble sticks or plants, and so escape notice. 



b. Aggressive resemblances ; the purpose of 



which is to aid the approach to prey ; for 

 example the resemblance of the colour of 

 the lion to that of the desert. 



