Universality of the caress, of amorous preludes.--Their rôle in fecundation.--Sexual games of birds.--How cantharides caress.--Males' combats.--Pretended combats of birds.--Dance of the tetras.--Gardener bird.--His country house.--His taste for flowers.--Reflections on the origin of his art.--Combats of crickets.--Parade of butterflies.--Sexual sense of orientation.--The great-peacock moth.--Animals' submission to orders of Nature.--Transmutation of physical values.--Rutting calendar. XVI. Polygamy Rarity of monogamy.--Taste for change in animals.--Rôles of monogamy and polygamy in the stability or instability of specific types.--Strife of the couple against polygamy. --Couples among insects.--Among fish, batrachians, saurians. --Monogamy of pigeons, of nightingales.--Monogamy in carnivora, in rodents.--Habits of the rabbit.--The ichneumon.--Unknown causes of polygamy.--Rarity and superabundance of males. --Polygamy in insects.--In fish.--In gallinaceæ, in web-footed birds.--In herbivora.--The antelope's harem.--Human polygamy. --How it tempera the couple among civilized races. XVII. Love among Social Animals Organization of reproduction among hymenoptera.--Bees.--Wedding of the queen.--Mother bee, cause and consciousness of the hive. --Sexual royalty.--Limits of intelligence among bees.--Natural logic and human logic.--Wasps.--Bumble-bees.--Ants.--Notes on their habits.--Very advanced state of their civilization. --Slavery and parasitism among ants.--Termites.--The nine principal active forms of termites.--Great age of their civilization.--Beavers.--Tendency of industrious animals to inactivity. XVIII. The Question of Aberrations Two sorts of sexual aberration.--Sexual aberrations of animals. --Those of men.--Crossing of species.-- Chastity.--Modesty. --Varieties and localizations of sexual bashfulness.--Artificial creation of modesty.--Sort of modesty natural to all females. --Cruelty.--Picture of carnage.--The cricket eaten alive. --Habits of carabes.--Every living creature is a prey. --Necessity to kill or to be killed. XIX Instinct Instinct.--Can one oppose it to intelligence?--Instinct in man. --Primordiality of intelligence.--Instinct's conservative rôle. --Modifying rôle of intelligence.--Intelligence and consciousness. --Parity of animal and human instinct.--Mechanical character of the instinctive act.--Instinct modified by intelligence.--Habit of work creates useless work.--Objections to the identification of instinct and intelligence taken from life of insects. XX. Tyranny of the Nervous System