258 
THE PKINCIPLES OP 
Part XI- 
possessed by the males for fighting with and driving 
away their rivals — their courage and pugnacity — their 
ornaments of many kinds — their organs for producing 
vocal or instrumental music — and their glands for 
emitting odours; most of these latter structures serv- 
ing only to allure or excite the female. That these 
characters are the result ol sexual and not of ordinary 
selection is clear, as unarmed, unornamented, or un- 
attractive males would succeed equally well in the 
battle for liie and in leaving a numerous progeny, if 
better endowed males were not present. We may infer 
that this would be the case, for the females, which are 
unarmed and unornamented, are able to survive and 
procreate their kind. Secondary sexual characters of 
the kind just referred to, will be fully discussed in the 
following chapters, as they are in many respects in' 
teresting, but more especially as they depend on the 
will, choice, and rivalry of the individuals of either sex. 
W hen we behold tw r o males lighting for the possession 
of the female, or several male birds displaying their 
gorgeous plumage, and performing the strangest antics 
before an assembled body of females, we cannot doubt 
that, though led by instinct, they know what they are 
about, and consciously exert their mental and bodily 
powers. 
In the same manner as man can improve the breed 
of his game-cocks by the selection of those birds which 
are victorious in the cockpit, so it appears that the 
strongest and most vigorous males, or those provided 
with the best weapons, have prevailed under nature? 
and have led to the improvement of the natural breed 
or species. Through repeated deadly contests, a slight 
degree ol variability, if it led to some advantage, how- 
ever slight, would suffice for the work of sexual selec- 
tion ; and it is certain that secondary sexual characters 
