Finding with their host both food and lodging, they throw off their fishing and travelling gear, settle themselves comfortably in the organs which they have chosen, and having got rid of the baggage which connected them with the outer world, preserve only their sexual organs. As to the rank which these parasites occupy in the scale of being, it may be said that there is no especial class of parasites; and worms are not distinguished in this respect, except by having a greater number of species subject to this rule. All classes among invertebrate animals include parasites. It is also an error to suppose that the whole species, the young as well as the old, the males as well as the females, are always parasites; often the female, not being able to provide for the necessities of life, seeks for food and shelter, while the male continues his nomad life. Therefore the female alone puts on the pauper's dress, and by a recurrent development, assumes sometimes such a singular appearance that the male no longer resembles her. One cannot say that the females constitute the _beau sexe_ in this group, since they are often so monstrous in form and size that their appearance has nothing in common with a perfect animal; their body is deprived of all its exterior organs, and there often remains only a skin in the form of a leather bag, without any distinguishing character. What is still more astonishing, is to meet with males which, under the 89 conditions to which we have just alluded, come at last to seek for assistance from their own female, so that she has to provide for all; and the charitable animal which comes to her help takes the whole family under his charge. Assistance is thus thoroughly organized in the lower world; neighbours are found which serve as a _crèche_ for the indigent when they first quit the egg, others as a hospital for the infirm adults or the females, and others again play the part of innkeepers for all, instead of affording a place of refuge for some privileged individuals. There are but few animals, if indeed there are any, which have not their peculiar parasites. Of all the fishes of our coasts we have never found but one which had none; and perhaps, could we observe this fish in different latitudes, we might find that it had its poor dependants as well as the rest.