Slight influence of the direct action of the conditions of life--Slight or
no influence of natural selection--Sexual selection.


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-- The proportion of the sexes in relation to natural
selection.


CHAPTER IX.

Secondary Sexual Characters in the Lower Classes of the Animal Kingdom.

These characters are absent in the lowest classes--Brilliant colours--
Mollusca--Annelids--Crustacea, secondary sexual characters strongly
developed; dimorphism; colour; characters not acquired before maturity--