But no batrachian patience is as curious as that of the pipa toad. This is a hideous beast with small eyes, mouth surrounded with whisker-prickles, skin blackish green, full of warts and swellings. As the eggs are laid the male fecundates them, then taking them in his large webbed feet he spreads them out on the female's back. Around each egg there forms a little protective pustule, in which the young hatch. The female on whom a hatch commences offers the odd spectacle of a back whence, here and there, heads and feet are sprouting, or from which emerge little toads as if born of a paradox.[2] This formation is another proof that nature finds anything good which happens to attain her purpose, and that she cares only for the perpetuation of life. An incubatorial pocket was necessary, and she had forgotten it; no matter, the animal will make one for itself, at its own expense or at the expense of some other specie. The small pipas exercize a real parasitism, ordered by an absent-mindedness of nature. Whether the deposit of eggs be in the mother's back or in the tissue of some other animal the parasitism is no less evident, at most it is a question of degree. From this point of view it will be possible to consider the normal, internal evolution of sexual products as a parasitic evolution: the young of the mammal is a parasite of its mother, as the little ichneumon is a parasite of the caterpillar which serves it as uterus. Thus considered the notion of parasitism temporary or larval will disappear, or, rather, take a much greater extension, enveloping a considerable number of facts up till now separated in irreducible categories. Fecundation by contact is very rare in fish, other than selacians. One hardly finds it save in lophobranchi and certain other viviparous fish, such as the blenny; the milt penetrates the female organs without copulation, and the eggs develop either in these organs, or in a pouch which the male carries under his belly, or even in the male's mouth, he having thus the virtue of assuring the birth of his offspring. The lophobranchi are wholly singular fish, one of them, the sea-horse, horse-headed ludion, gives a good idea of the family. Ordinary fish, such as one knows and eats, however M. de Lacépède may have classified them, are chaste animals void of all erotic fantasy.