CHAPTER VIII 
SEXUAL COLOUR 
Mates 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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