SEXUAL SELECTION. 203 



PART II. 



SEXUAL SELECTION. 



CHAPTER VIII. 



PRINCIPLES OP SEXUAL SELECTION. 



Secondary sexual characters— Sexual selection — Manner of action- 

 Excess of males — Polygamy— The male alone generally modified 

 through sexual selection— Eagerness of the male — Variability of 

 the male — Choice exerted by the female— Sexual compared with 

 natural selection— Inheritance, at corresponding periods of life, 

 at corresponding seasons of the year, and as limited by sex— Re- 

 lations between the several forms of inheritance — Causes why one 

 sex and the young are not modified through sexual selection— Sup- 

 plement on the proportional numbers of the two sexes throughout 

 the animal kingdom— The proportion of the sexes In relation to 

 natural selection. 



With animals which have their sexes separated, the males 

 necessarily differ from the females in their organs of reproduc- 

 tion; and these are the primary sexual characters. But the 

 sexes often differ in what Hunter has called secondary sexual 

 characters, which are not directly connected with the act of re- 

 production; for instance, the male possesses certain organs of 

 sense or locomotion, of which the female Is quite destitute, or has 

 them more highly-developed, in order that he may readily find or 

 reach her; or again the male has special organs of prehension 

 for holding her securely. These latter organs, of infinitely di- 

 versified kinds, graduate into those which are commonly ranked 

 as primary, and in some cases can hardly be distinguished from 

 them; we see instances of this in the complex appendages at the 

 apex of the abdomen in male insects. Unless indeed we confine 

 the term "primary" to the reproductive glands, it Is scarcely 

 possible to decide which ought to be called primary and which 

 secondary. 



The female often differs from the male in having organs for 



