SEXUAL SELECTION. 257 



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 expending 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 won- 

 derful 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 con- 

 quering 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 adaptation to their condi- 

 tions 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. i 



Latos 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 

 distinction 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 sexual characters 

 are crossed, for each transmits the characters proper to its 

 own male and female sex to the hybrid offspring of either 

 sex. The same fact is likewise manifest when characters 

 proper to the male are occasionally developed in the female 

 when she grows old or becomes diseased, as, for instance, 

 when tlie common hen assumes the flowing tail-feathers, 

 hackles, comb, spurs, voice, and even pugnacity of the 

 cock. Conversely the same thing is evident more or less 



