SEXUAL SELECTION 299 



spring. 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 pur- 

 poses; but in regard to structures adapted to make one male 

 victorious over another, either in fighting or in charming the 

 female, there is no definite limit ^o the amount of advanta- 

 geous modification ; so that as long as the proper variations 

 arise the work of sexual selection will go on. This circum- 

 stance may partly account for the frequent and extraordi- 

 nary amount of variability presented by secondary sexual 

 characters. Nevertheless, natural selection will determine 

 that such characters shall not be acquired by the victorious 

 males, if they would be highly injurious, either by expend- 

 ing too much of their vital powers, or by exposing them to 

 any great danger. The development, however, of certain 

 structures — of the horns, for instance, in certain stags — has 

 been carried to a wonderful extreme; and in some cases to 

 an extreme which, as far as the general conditions of life 

 are concerned, must be slightly injurious to the male. From 

 this fact we learn that the advantages which favored males 

 derive from conquering other males in battle or courtship, 

 and thus leaving a numerous progeny, are in the long run 

 greater than those derived from rather more perfect adapta- 

 tion to their conditions of life. We shall further see, and it 

 could never have been anticipated, that the power to charm 

 the female has sometimes been more important than the 

 power to conquer other males in battle. 



LAWS OF INHERITANCE 



In order to understand how sexual selection has acted 

 on many animals of many classes, and in the course of ages 

 has produced a conspicuous result, it is necessary to bear 

 in mind the laws of inheritance, as far as they are known. 

 Two distinct elements are included under the term "inheri- 

 tance" — the transmission and the development of characters; 



