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Part IL 

 SEXUAL SELECTION. 



CHAPTEE Vin. 

 Principles of Sexual Sblection. 



Secondary sexual charaoters — Sexual selection — Manner of action — Ex- 

 cess of -males — Polygamy — The male alone gunerally 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 — The proportion of the 

 sexes in relation to natural selection. 



^\"iTH animals which have their sexes separated, the males 

 necessarily differ from the females in their organs of reproduction ; 

 and these are the primary sexual charaoters. But the sexes 

 often differ in -what Hunter has called secondary sexual charac- 

 ters, which are not directly connected with the act of reproduc- 

 tion ; 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 diversified 

 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 

 tlie term " primary " to the reproductive glands, it is scarcely 

 possible to decide which ought to be called primary and which 

 Ecrondary. 



The female often differs from the male in having oigans for the 

 nourislimcnt or protection of her young, such as the maumiary 



