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.
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.
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.
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.
Accord and discord between organs and acts.--Tarses and sacred scarab.--The hand of man.--Mediocre fitness of sexual organs for copulation.--Origin of "luxuria."--The animal is a nervous system served by organs.--The organ does not determine the aptitude. --Man's hand inferior to his genius.--Substitution of one sense for another.--Union and rôle of the senses in love.--Man and animal under the tyranny of the nervous system.--Wear and tear of humanity compensated by² acquisitions.--Man's inheritors.