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 sexes, yet primarily acquired by the male--Other uses of such weapons--Their high importance-- Greater size of the male--Means of defence--On the preference shewn by either sex in the pairing of quadrupeds.

CHAPTER XVIII.

Secondary Sexual Characters of Mammals--continued.

Voice--Remarkable sexual peculiarities in seals--Odour--Development of the hair--Colour of the hair and skin--Anomalous case of the female being more ornamented than the male--Colour and ornaments due to sexual selection-- Colour acquired for the sake of protection--Colour, though common to both sexes, often due to sexual selection--On the disappearance of spots and stripes in adult quadrupeds--On the colours and ornaments of the Quadrumana--Summary.

PART III. SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.

CHAPTER XIX.

Secondary Sexual Characters of Man.

Differences between man and woman--Causes of such differences, and of certain characters common to both sexes--Law of battle--Differences in mental powers, and voice--On the influence of beauty in determining the marriages of mankind--Attention paid by savages to ornaments--Their ideas of beauty in women--The tendency to exaggerate each natural peculiarity.

CHAPTER XX.

Secondary Sexual Characters of Man--continued.

On the effects of the continued selection of women according to a different standard of beauty in each race--On the causes which interfere with sexual selection in civilised and savage nations--Conditions favourable to sexual selection during primeval times--On the manner of action of sexual selection with mankind--On the women in savage tribes having some power to choose their husbands--Absence of hair on the body, and development of the beard--Colour of the skin--Summary.

CHAPTER XXI.

General Summary and Conclusion.

Main conclusion that man is descended from some lower form--Manner of development--Genealogy of man--Intellectual and moral faculties--Sexual selection--Concluding remarks.

SUPPLEMENTAL NOTE.

INDEX.

The Descent of Man Page 04

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Charles Darwin

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