210 EVOLUTION OF TO-DA F. 



sess a variation which gives it some special advan- 

 tage for obtaining food or fighting with its enemies, 

 this individual will have a much better chance than 

 others for reaching maturity and leaving offspring. 

 The animals best fitted to the conditions will sur- 

 vive, while others will perish. This is natural selec- 

 tion. (4) It is an unquestioned law, that animals 

 transmit to their offspring their own characteristics, 

 and, therefore, the individuals naturally selected by 

 means of these favorable variations will transmit 

 these same variations, and, as a result, we should 

 find that nearly all of the next generation would 

 possess the advantages of their parents. During the 

 succeeding generations, the same selection will be 

 enforced, so that shortly all of the -unfavored indi- 

 viduals will disappear. As this process of selection 

 goes on, the peculiarities which give advantage will 

 become more and more prominent, and thus a new 

 variety of the old species will arise, which, still later, 

 will become more marked, and finally will be a new 

 species. 



In order to explain the differences which are fre- 

 quently found in the two sexes, Darwin supplements 

 natural selection with another principle which he 

 calls Sexual Selection. He shows that among many 

 animals there is a contest during the breeding season 

 among the males for the possession of the females, 

 a contest sometimes by actual combats, and some- 

 times by an attempt to attract the favor of the 

 females by the display of brilliant plumage, or by 

 singing. In all of these cases the victor in the 

 contest mates with the more vigorous females, and 



