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 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 supply of blood 
to these parts being at a maximum, the erection of the plumes 
woidd 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 sesthetic 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 production of accessory 
ornamental plumes, I have elsewhere suggested 1 that crests 
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 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 Avhich enable most of their possessors to defend them¬ 
selves against the enemies which 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 by 
Natural Selection. 
The various facts and arguments now briefly set forth, 
afford an explanation of the phenomena of male ornament, 
1 Tropical Nature, p. 209. In Chapter V of this work the views here 
advocated were first set forth, and the reader is referred there for further 
details. 
