222 THE DESCENT OP IIAN. 



not rarely ensues from the conflicts of rival males. But generally 

 the less successful male merely fails to obtain a female, or obtains 

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

 amous, obtains fewer females; Po that they leave fewer, less vig- 

 orous, 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 ad- 

 vantageous modification in relation to certain special purposes; 

 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 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 partly account for 

 the frequent and extraordinary 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 ex- 

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

 any great danger. The development, however, of certain struct- 

 ures — of the horns, for instance, in certain stags — has been car- 

 ried 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 prog- 

 eny, are in the long run greater than those derived from rather 

 more perfect adaptation to their conditions of life. We shall fur- 

 ther 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 "inheritance" — the transmission, 

 and the development of characters; but as these generally go 

 together, the distinction is often overlooked. We see this dis- 

 tinction in those characters which are transmitted through the 

 early years of life, but are developed only at maturity or during 

 old age. We see the same distinction more clearly with secondary 

 sexual characters, for these are transmitted through both sexes, 

 though developed in one alone. That they are present in both 

 sexes, is manifest when two species, having strongly-marked sex- 

 ual characters, are crossed, for each transmits the characters prop- 



