Page:Descent of Man 1875.djvu/13

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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 207

Chapter IX.
Secondary Sexual Characters in the Lower Classes of the Animal Kindgom.
These characters 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 260

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 colours — Coleoptera, colours; furnished with great horns, apparently as an ornament; battles; stridulating organs generally common to both sexes 274