278 
THE PRINCIPLES OP 
Part li- 
the acquirement through sexual selection of conspicuous 
colours, may have been checked from the danger thus 
incurred. But in other cases the males have probably 
struggled together during long ages, through brute 
force, or by the display of their charms, or by both 
means combined, and yet no effect will have been pro* 
duced unless a larger number of offspring were left by 
the more successful males to inherit their superiority, 
than by the less successful males ; and this, as previously 
shown, depends on various complex contingencies. 
Sexual selection acts in a less rigorous manner than 
natural selection. The latter produces its effects by the 
life or death at all ages of the more or less successful 
individuals. Death, indeed, not rarely ensues from the 
conflicts of rival males. But generally the less success- 
ful male merely fails to obtain a female, or obtains a 
retarded and less vigorous female later in the season, 
or, if polygamous, obtains fewer females ; so that they 
leave fewer, or less vigorous, or no offspring. In re- 
gaid to structures acquired through ordinary or natural 
selection, there is in most cases, as long as the condi- 
tions of life remain the same, a limit to the amount of 
advantageous modification in relation to certain special 
ends ; but in regard to structures adapted to make one 
male victorious over another, either in fighting or i» 
charming the female, there is no definite limit to the 
amount of advantageous modification ; so that as long & 
the proper variations arise the work of sexual selection 
will go on. This circumstance may partly account for 
the frequent and extraordinary amount of variability 
presented by secondary sexual characters. Nevertheless, 
natural selection will determine that characters of this 
kind shall not be acquired by the victorious malts, 
which would be injurious to them in any high degree, 
either by expending too much of their vital powers, or 
