NATURAL SELECTION 81 



believe that there is the severest rivalry between the 

 males of many species to attract by singing- the females. 

 The rock-thrush of Guiana, birds of Paradise, and some 

 others, congregate ; and successive males display their 

 gorgeous plumage and perform strange antics before the 

 females, which, standing by as spectators, at last choose 

 the most attractive partner. Those who have closely 

 attended to birds in confinement well know that they 

 often take individual preferences and dislikes : thus 

 Sir R. Heron has described how one pied peacock was 

 eminently attractive to all his hen birds. It may 

 appear childish to attribute any effect to such appar- 

 ently weak means : I cannot here enter on the details 

 necessary to support this view ; but if man can in a short 

 time give elegant carriage and beauty to his bantams, 

 according to his standard of beauty, I can see no good 

 reason to doubt that female birds, by selecting, during*- 

 thousands of generations, the most melodious or beau- 

 tiful males, according to their standard of beauty, 

 might produce a marked effect. I strongly suspect 

 that some well-known laws, with respect to the plumage 

 of male and female birds, in comparison with the 

 plumage of the young, can be explained on the view 

 of plumage having been chiefly modified by sexual 

 selection, acting when the birds have come to the 

 breeding age or during the breeding season ; the 

 modifications thus produced being inherited at corre- 

 sponding ages or seasons, either by the males alone, or 

 by the males and females ; but I have not space here 

 to enter on this subject. 



Thus it is, as I believe, that when the males and 

 females of any animal have the same general habits 

 of life, but differ in structure, colour, or ornament, 

 such differences have been mainly caused by sexual 

 selection ; that is, individual males have had, in 

 successive generations, some slight advantage over 

 other males, in their weapons, means of defence, or 

 charms ; and have transmitted these advantages to 

 their male offspring. Yet, I would not wish to attri- 

 bute all such sexual differences to this agency : for we 



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