s, 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 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
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[134] 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 development, 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 themselves 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, as being due to the
general laws of growth and development, and make it unnecessary to call
to our aid so hypothetical a cause as the cumulative action of female
preference. There remains, however, a general argument, arising from the
action of natural selection itself, which renders it almost
inconceivable that female preference could have been effective in the
way suggested; while the same argument strongly supports the v