282 THE BIRD WATCHER 
of direct evidence, fogghow otherwise could the breed- 
ing be accomplished? Then what a most extra- 
ordinary thing it would be if she were excited in 
precisely the same degree—not one jot or tittle more 
_ or less—by any one male as by any other! Whatever 
the nature of that sexual appeal may be which every 
cock makes to every hen, and by virtue of which she 
feels that he is a cock, and not a hen like herself, 
why should we suppose that any two individuals 
should be more exactly alike in it than they are in 
anything else? But if there is not this absolute 
unity, then there is difference, and such difference 
in the degree of the sexual charm flung out by each 
male, must produce preference and choice in the female. 
The whole theory of evolution is based upon the 
undisputed and indisputable fact of individual varia- 
bility ; nor is there any one thing or quality, bodily 
or mental—amongst the higher animals at least—that 
does not vary largely in the different individuals 
possessing it. As it appears to me, therefore, choice 
in the one sex with regard to the other is what might 
have been, on a@ priori considerations, expected ; 
though I can well understand that, as amongst our- 
selves, it would often be held in abeyance, or nullified, 
by the operation of higher—that is to say, more 
inexorable—laws, and also that its manifestations 
would often be too subtle and hidden for us to follow 
them. But we first, in deference to our human 
prejudices, assume something which is improbable 
in itself, and then obstinately resist a mass of the 
