Sexual dimorphism and parallelism.--Sexual organs of man and of woman.--Constancy of sexual parallelism in the animal series.--External sexual organs of placentary mammifera. --Form and position of the penis.--The penial bone.--The clitoris.--The vagina.--The teats.--Forked prong of marsupials. --Sexual organs of reptiles.--Fish and birds with a penial organ.--Genital organs of arthropodes.--Attempt to classify animals according to the disposition, presence, absence of exterior organs for reproduction. IX. The Mechanism of Love 1. Copulation: Vertebrates.--Its very numerous varieties and its specific fixity.--The apparent immorality of Nature. --Sexual ethnography.--Human mechanism.--Cavalage.--The form and duration of coupling in divers mammifers.--Aberrations of sexual surgery, the ampallang.--Pain as a bridle on sex. --Maidenhead.--The mole.--Passivity of the female.--The ovule, psychological figure of the female.--Mania of attributing human virtues to animals.--The modesty of elephants.--Coupling mechanism in whales, seals, tortoises.--In certain ophidians and in certain fish. X. The Mechanism of Love 2. Copulation (Continued)--Arthropodes.--Scorpions.--Large aquatic crustaceans.--Small crustaceans.--The hydrachne. --Scutilary.--Cockchafer.--Butterflies.--Flies, etc.--Variation of animals' sexual habits. XI. The Mechanism of Love p. 98 3. Of birds and fish.--Males without penis.--Coupling by simple contact.--Salacity of birds.--Copulation of batrachians: accoucheur toad, aquatic toad, earth toad, pipa toad.--Fœtal parasitism.--Chastity of fish.--Sexes separated in love. --Onanistic fecundation.--Cephalopodes, the spermatophore. XII, The Mechanism of Love 4. Hermaphrodism.--Sexual life of oysters.--Gasteropodes. --The idea of reproduction and the idea of pleasure.--Mechanism of reciprocal reproduction: helices.--Spintrian habits. --Reflection on hermaphrodism. XIII. The Mechanism of Love 5. Artificial fecundation.--Disjunction of the secreting apparatus from the copulating apparatus.--Spiders.--Discovery of their copulative method.--Brutality of the female.--Habits of the epeire.--The argyronete.--The tarantula.--Exceptions: the reapers.--Dragonflies (libellule).--Dragonflies (demoiselle) virgins and "jouvencelle."--Picture of their love affairs. XIV. The Mechanism of Love 6. Cannibalism in sex.--Females who devour the male, those who devour the spermatophore.--Probable use of these practices.--Fecundation by the whole male.--Loves of the white foreheaded dectic.--The green grasshopper.--The Alpine analote.--The ephippigere.--Further reflections on the cannibalism of sex.--Loves of the praying mantis. XV. The Sexual Parade