294 DARWINISM chap. 



train that has led to the broadening of the feathers at the 

 ends, and the consequent production of the magnificent eye- 

 spots which now form its crowning ornament. 



The disphiy of these pkimes will result from the same 

 causes which led to their production. Just in proportion as 

 the feathers themselves increased in length and abundance, the 

 skin-muscles which serve to elevate them Avould increase also ; 

 and the nervous development as well as the supply of blood 

 to these parts being at a maximum, the erection of the plumes 

 "would become a habit at all periods of nervous or sexual 

 excitement. The display of the plumes, like the existence of 

 the plumes themselves, would be the chief external indication 

 of the maturity and vigour of the male, and would, therefore, 

 be necessarily attractive to the female. We have, thus, no 

 reason for imputing to her any of those aesthetic emotions 

 which are excited in us, by the beauty of form, colour, and 

 pattern of these plumes ; or the still more improbable i>?sthetic 

 tastes, which would cause her to choose her mate on account 

 of minute differences in their forms, colours, or patterns. 



As co-operating causes in the production of accessory 

 ornamental plumes, I have elsewhere suggested ^ that crests 

 1 and other erectile feathers may have been useful in making 

 the bird more formidable in appearance, and thus serving to 

 frighten away enemies ; while long tail or ■\ving feathers might 

 serve to distract the aim of a bird of prey. But though this 

 might be of some use in the earlier stages of their develop- 

 ment, it is probably of little importance compared with the 

 vigour and pugnacity of Avhich the plumes are the indication, 

 and which enable most of their possessors to defend them- 

 selves against the enemies Avhich are dangerous to weaker 

 and more timid birds. Even the tiny humming-birds are said 

 to attack birds of prey that approach too near to their nests. 



The Effect of Female Preference will be Neutralised hy 

 Natural Selection. 



The various facts and arguments now l)riefly set forth, 

 afford an explanation of the phenomena of male ornament, 



^ Tropical JVature, p. 209. In Chapter Y of this work the views here 

 advocateil were first set forth, and the reader is referred there for further 

 details. 



