Fishes: Courtship and battles of the males Larger size of the
females Males, bright colours and ornamental appendages; other strange
characters Colours and appendages acquired by the males during the
breeding-season alone Fishes with both sexes brilliantly
coloured Protective colours The less conspicuous colours of the female
cannot be accounted for on the principle of protection Male fishes
building nests, and taking charge of the ova and young. AMPHIBIANS:
Differences in structure and colour between the sexes Vocal organs.
REPTILES: Chelonians Crocodiles Snakes, colours in some cases
protective Lizards, battles of Ornamental appendages Strange
differences in structure between the sexes Colours Sexual differences
almost as great as with birds.
CHAPTER XIII.
SECONDARY SEXUAL CHARACTERS OF BIRDS.
Sexual differences Law of battle Special weapons Vocal
organs Instrumental music Love-antics and dances Decorations, permanent
and seasonal Double and single annual moults Display of ornaments by
the males.
CHAPTER XIV.
BIRDS continued.
Choice exerted by the female Length of courtship Unpaired birds Mental
qualities and taste for the beautiful Preference or antipathy shewn by
the female for particular males Variability of birds Variations
sometimes abrupt Laws of variation Formation of ocelli Gradations of
character Case of Peacock, Argus pheasant, and Urosticte.
CHAPTER XV.
BIRDS continued.
Discussion as to why the males alone of some species, and both sexes of
others are brightly coloured On sexually-limited inheritance, as
applied to various structures and to brightly-coloured
plumage Nidification in relation to colour Loss of nuptial plumage
during the winter.
CHAPTER XVI.
BIRDS concluded.
The immature plumage in relation to the character of the plumage in
both sexes when adult Six classes of cases Sexual differences between
7