70 SEXUAL SELECTION. [Chap. IV- 



All those who have attended to the subject, 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 with the most 

 elaborate care, and show off in the best manner their gorgeous plu- 

 mage; they likewise 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 kno-w 

 that they often take individual preferences and dislikes: thus Sir K. 

 Heron has described how a pied peacock was eminently attractive to 

 all his hen birds. I cannot nere enter on the necessary details ; but 

 if man can in a short time give beauty and an elegant carriage 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 beautiful males, according to their 

 standard of beauty, might produce a marked effect. Some well- 

 known laws, with respect to the plumage of male and female birds.. 

 in comparison with the plumage of the young, can partly be ex- 

 plained through the action of sexual selection on variations occurring 

 at different ages, and transmitted to the males alone or to both sexes 

 at corresponding ages ; 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, by individual males having had, in suc- 

 cessive generations, some slight advantage over other males, in their 

 weapons, means of defence, or charms, which they have transmitted 

 to their male offspring alone. Yet, I would not wish to attribute all 

 sexual differences to this agency : for we see in our domestic animals 

 peculiarities arising and becoming attached to the male sex, which 

 apparently have not been augmented through selection by man. 

 The tuft of hair on the breast of the wild turkey-cock cannot be of 

 any use, and it is doubtful whether it can be ornamental in the eyes 

 of the female bird ; — indeed, had the tuft appeared under domestica- 

 tion, it would have been called a monstrosity. 



Illustrations of the Action of Natural Selection, or the Survival 

 of the Fittest, 



In order to make it clear how, as I believe, natural selection acts, 

 I must beg permission to give one or two imaginary illustrations. 

 Let us take the case of a wolf, which preys on various animals, 

 securing some by craft, some by strength, and some by fleetnees ; 



