The Descent of Man | Page 5

tribe--Natural selection as affecting civilised nations--Evidence that civilised nations
were once barbarous.

CHAPTER VI.
On the Affinities and Genealogy of Man.
Position of man in the animal series--The natural system genealogical-- Adaptive
characters of slight value--Various small points of resemblance between man and the
Quadrumana--Rank of man in the natural system-- Birthplace and antiquity of
man--Absence of fossil connecting-links--Lower stages in the genealogy of man, as
inferred firstly from his affinities and secondly from his structure--Early androgynous
condition of the Vertebrata --Conclusion.

CHAPTER VII.
On the Races of Man.
The nature and value of specific characters--Application to the races of man--Arguments
in favour of, and opposed to, ranking the so-called races of man as distinct
species--Sub-species--Monogenists and polygenists-- Convergence of
character--Numerous points of resemblance in body and mind between the most distinct
races of man--The state of man when he first spread over the earth--Each race not
descended from a single pair--The extinction of races--The formation of races--The
effects of crossing-- 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-- Spiders, sexual colours of;
stridulation by the males--Myriapoda.

CHAPTER X.
Secondary Sexual Characters of Insects.
Diversified structures possessed by the males for seizing the females-- Differences
between the sexes, of which the meaning is not understood-- Difference in size between
the sexes--Thysanura--Diptera--Hemiptera-- Homoptera, musical powers possessed by
the males alone--Orthoptera, musical instruments of the males, much diversified in
structure; pugnacity; colours--Neuroptera, sexual differences in colour--Hymenoptera,
pugnacity and odours--Coleoptera, colours; furnished with great horns, apparently as an
ornament; battles; stridulating organs generally common to both sexes.

CHAPTER XI.
Insects, continued.--Order Lepidoptera.
(Butterflies and Moths.)
Courtship of Butterflies--Battles--Ticking noise--Colours common to both sexes, or more
brilliant in the males--Examples--Not due to the direct action of the conditions of
life--Colours adapted for protection--Colours of moths--Display--Perceptive powers of
the Lepidoptera--Variability-- Causes of the difference in colour between the males and
females--Mimicry, female butterflies more brilliantly coloured than the males--Bright
colours of caterpillars--Summary and concluding remarks on the secondary sexual
character of insects--Birds and insects compared.

CHAPTER XII.
Secondary Sexual Characters of Fishes, Amphibians, and Reptiles.
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 the males of closely-allied or
representative species--The female assuming the characters of the male--Plumage of the
young in relation to the summer and winter plumage of the adults--On the increase of
beauty in the birds of the world--Protective colouring--Conspicuously coloured
birds--Novelty appreciated--Summary of the four chapters on birds.

CHAPTER XVII.
Secondary Sexual Characters of Mammals.
The law of battle--Special weapons, confined to the males--Cause of absence of weapons
in the female--Weapons common to both