One ought, at the end of this summary chapter, to be courageous enough to say that fecundation, as vulgarly understood, is merely an illusion. Taking man and woman (or no matter what dioic metazoaire) the man does not fecundate the woman; what happens is at once more mysterious and more simple. From the male A, the great Male, and from the great Female B are born without any fecundation whatever, spontaneously, little males a and little females 6. These little males are called spermatozoides, and the little females, ovules; it is between these new creatures, between these spores, that the fecundating union occurs. One then observes that _a_ and _b_ resolve themselves into a third animal _x_, which by natural growth becomes either A or B. Then the cycle begins again. The union between A and B is merely a preparation; A and B are nothing but channels carrying _a_ and _b_, carrying them often far beyond themselves. Like the plant-lice or drones, the mammifers called man are subject to alternate generation, one parthenogenesis always separating the veritable conjunction of the differentiated elements. Coupling is not fecundation; it is merely the mechanism; its utility is merely in that it puts two parthenogenetic products into relation. This relation occurs inside the female, or outside the female (as in case of fishes); the milieu has an importance of fact, not of principle. CHAPTER IV SEXUAL DIMORPHISM I. Invertebrates: formation of the male.--Primitivity of the female.--Minuscule males: the bonellie. --Regression of the male into the male organ: the cirripedes.--Generality of sexual dimorphism.--Superiority of the female in most insect species.--Exceptions.--Numeric dimorphism.--Female hymenoptera.--Multiplicity of her activities.--Male's purely sexual rôle.-- Dimorphism of ants and termites.--Grasshoppers and crickets.--Spiders.--Coleoptera.--Glow-worm. --Cochineal's strange dimorphism. I. Invertebrates.--At a moment fairly undecided in the general evolution the male organ specializes into the male individual. Religious symbolisms may or might have been intended to mean this. The female is primitive. At the third month, the human embryo has external uro-genital organs clearly resembling the female organs. To arrive at complete female estate they need undergo but a very slight modification; to become male they have to undergo a considerable and very complex transformation. The external genital organs of the female are not, as has been often said, the product of an arrested development; quite the contrary, the male organs undergo a supplementary development, which is moreover useless, for the penis is a luxury and a danger: the bird who does without it is no less wanton thereby.