138 Permanence and Evolution. 



coloured would have an advantage, and would 

 gradually supplant the others, there being no 

 reason why they should have less of any other 

 protection. 



Here comes in the theory of sexual selection 

 by which it is supposed that female animals, 

 especially birds, prefer the brightest coloured 

 males, who consequently when (having some 

 other protection) they are not absolutely 

 stopped by natural selection, have more progeny 

 than others, etc. We shall, I think, see later that 

 there is no evidence for this preference of 

 females ; but if it were a fact, it could be no 

 more permanent or immutable than anything 

 else in the animal constitution, mental or 

 physical ; it must have been acquired, and 

 acquired too in the teeth of natural selection, 

 because those strains of animals whose females 

 had a taste for less gaudy and more useful 

 coloured mates, would gradually supplant those 

 families whose females had more frivolous tastes, 



