modification of the same form as that from which the other Primates
have sprung.
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.
With animals which 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 in what
Hunter has called secondary sexual characters, which are not directly
connected with 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 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 the term primary to
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