SEXUAL SELECTION. 273 



As variations which give to the male a better cliance of 

 conquering other males or of finding, securing or charm- 

 ing the opposite sex would, if they happened to arise in the 

 female, be of no service to her, they would not be pre- 

 served in her through sexual selection. We have also good 

 evidence with domesticated animals that variations of all 

 kinds are, if not carefully selected, soon lost through inter- 

 crossing and accidental deaths. Consequently in a state 

 of nature if variations of the above kind chanced to arise 

 in the female line, and to be transmitted exclusively in 

 this line, they would be extremely liable to be lost. If, 

 however, the females varied and transmitted their newly 

 acquired characters to their offspring of both sexes the 

 characters which were advantageous to the males would be 

 preserved by them through sexual selection, and the two 

 sexes would in consequence be modified in the same man- 

 ner, although such characters were of no use to the 

 females; but I shall hereafter have to recur to these more 

 intricate contingencies. Lastly, the females may acquire 

 and apparently have often acquired by transference char- 

 acters from the male sex. 



As variations occurring late in life and transmitted to 

 one sex alone have incessantly been taken advantage of and 

 accumulated through sexual selection in relation to the 

 reproduction of the species; therefore it appears, at first 

 sight, an unaccountable fact that similar variations have 

 not frequently been accumulated through natural selection, 

 in relation to the ordinary habits of life. If this had 

 occurred, the two sexes would often have been differently 

 modified, for the sake, for instance, of capturing prey or 

 of escaping from danger. Differences of this kind between 

 the two sexes do occasionally occur, especially in the lower 

 classes. But this implies that the two sexes follow different 

 habits in their struggles for existence, which is a rare cir- 

 cumstance with the higher animals. The case, however, is 

 widely different with the reproductive functions, in which 

 respect the sexes necessarily differ. For variations in 

 structure, which are related to these functions, have often 

 proved of value to one sex, and from having arisen at a late 

 period of life, have been transmitted to one sex alone; and 

 such variations, thus preserved and transmitted, have given 

 rise to secondary sexual characters. 



In the following chapters 1 shall treat of the secondary 



