CHAPTEE VIII 



SEXUAL COLOUR 



MALES and females are frequently coloured 

 differently. With comparatively few excep- 

 tions, the males are more brightly coloured, 

 especially during the breeding season. These 

 characters are widely distributed throughout 

 the animal kingdom, and this universality 

 indicates that the cause must be of a world- 

 wide nature. In some cases it has been 

 observed that the sexes occupy either entirely, 

 or somewhat different, environments, hence 

 their colour differences. 



But in other cases, environmental differ- 

 ences, corresponding to these colour and 

 other structural differences, have not been 

 found. For this reason other theories have 

 been propounded to account for them. 



Darwin's sexual selection is the most gener- 

 ally accepted theory. This states that females 

 select males which have characters pleasing 

 to them, bright colours for instance. Assume 



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