Chap. VIII.] SEXUAL SELECTION. 2G9 



eolors have often been acquired through natural selection 

 for the sake of protection, and the acquirement through 

 sexual selection of conspicuous colors, 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 produced unless a larger number of off- 

 spring 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 maimer than 

 natural selection. The latter produces its effects by the 

 life or death at all as;es of the more or less successful 

 individuals. Death, indeed, not rarely ensues from the 

 conflicts of rival males. But generally the less successful 

 male merely fails to obtain a female, or obtains later in 

 the season a retarded and less vigorous female, or, if polyg- 

 amous, obtains fewer females ; so that they leave fewer, 

 or less vigorous, or no offspring. In regard to structures 

 acquired through ordinary or natural selection, there is in 

 most cases, as long as the conditions of life remain the 

 same, a limit to the amount of advantageous modification 

 in relation to certain special ends ; but in regard to struct- 

 ures adapted to make one male victorious over another, 

 either in fighting or in charming the female, there is no 

 definite limit to the amount of advantageous modification ; 

 so that as long as the proper variations arise the work of 

 sexual selection will go on. This" circumstance may part- 

 ly account for the frequent and extraordinary amount 

 of variability presented by secondary sexual characters. 

 Nevertheless, natural selection will determine that charac- 

 ters of this kind shall not be acquired by the victorious 

 males, which would be injurious to them in any high 



