Part II.— SEXUAL SELECTION. 



CHAPTER VIII. 



Principles of 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 — 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 — On the limita- 

 tion of the numbers of the two sexes through natural selection. 



With animals which have their sexes separated, the 

 males necessarily differ from the females in their organs 

 of reproduction ; and these afford 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 reproduction; for 

 instance, in the male possessing certain organs of sense 

 or locomotion, of which the female is quite destitute, or 

 in having them more highly-developed, in order that 

 he may readily find or reach her ; or again, in the male 

 having special organs of prehension so as to hold her 

 securely. These latter organs of infinitely diversified 

 kinds graduate into, and in some cases can hardly be 

 distinguished from, those which are commonly ranked 

 as primary, such as the complex appendages at the 

 apex of the abdomen in male insects. Unless indeed 



