PART TWO 

 SEXUAL SELECTIOM 



CHAPTEE VIII 



PRINCIPLES OF SEXUAL SELECTION 



Secondary sexual characters — Sexual selection — Manner of action — Excess 

 of males — Polygamy — The male alone generally modifled , throug^i 

 sexual selection — Eagerness of the male — Variability of the male — 

 Choice exerted by the female — Sexual compared with natural selec- 

 tion — Inheritance, at corresponding periods of life, at corresponding 

 seasons of the year, and as limited by sex — Relations between the 

 several forms of inheritance — Causes why one sex and the young are 

 not modified through sexual selection — Supplement on the proportional 

 numbers of the two sexes throughout the animal kingdom — The pro- 

 portion of the sexes in relation to natural selection 



WITH animals whicK have their sexes separated, the 

 males necessarily differ from the females in their 

 organs of reproduction; and these are the primary 

 sexual characters. But the sexes often differ ia what Hunter 

 has called secondary sexual characters, which are not di- 

 rectly connectedfiwith the act of reproduction ; 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 hold- 

 ing her securely. These latter organs, of infinitely diversi- 

 fied 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 appen<J* 

 ages at the apex of the abdomen- in male insects. Unless 

 indeed we confine the term "primary" to the reproductive 

 (274) 



