294 DARWINISM chap. 



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

 ends, and the consequent prochiction of the magnificent eye- 

 spots which now form its crowning ornament. 



The display of these plumes 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 would increase also ; 

 and the nervous development as well as the supj:)ly of Ijlood 

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

 would become a hal^it 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 aesthetic 

 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 j^roduction of accessory 

 ornamental plumes, I have elsewhere suggested ^ that crests 

 and other erectile feathers may have been useful in making 

 the bird more formida1)le in appearance, and thus ser\ang to 

 frighten away enemies ; while long tail or wing 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 which 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 he Neutralised hy 

 Natural Selection. 



The various facts and arguments now briefly set forth, 

 afford an explanation of the phenomena of male ornament, 



^ Tropical Nature, p. 209. In Cliapter V of this work the views here 

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

 details. 



