Fishermen affirm, and the examination of the animal's stomach confirms their assertion, that the _Cyclopterus lumpus_ feeds on nothing but the excreta of other fishes. Indeed, it is not possible to count the number of intestinal worms known by the name of _Scolex_, which are found in the contents of the stomach and the intestines. Besides this, we have long known the peculiarities of some insects which cannot live except on the dung of certain animals; and there is an example of one of these insects, found in a fossil state, which anticipated the discovery of the remains of an extinct mammal before unknown in that district. The larvæ of the fly _Scatophaga stercoraria_ live only on excrementary matter. There are also nematode worms which exist under these conditions, and which develop and propagate their species in the intestines as if in the midst of damp earth. The small eel-like creatures so abundant in cow-dung propagate in it; they are not parasites, and are allied to those of which we speak in this chapter. Besides those attendants which busy themselves about the cleanliness of other animals, we find some whose duties are less extensive, and whose cares are more limited. Many animals produce a greater number of eggs than they can bring to perfection, and those which are decomposed for want of fecundation, or which die in the course of evolution, 80 are under the care of an especial attendant, employed to make away from time to time with the addled eggs, or the embryos that have failed to come to maturity. In this manner lobsters give lodgings in the midst of their eggs to a worm, which we at first took for a Serpula, and which, after a complete examination, turns out to be one of the Hirudinidæ: we have given it the name of _Histriobdella_. It is as singular in its movements as in its conformation, and its manner of living approaches that of the _Pontobdellæ_ of the rays, of which we shall speak subsequently. We announced this discovery a few years ago in the following terms:--