and cross each other in every direction, but, be the wood ever so worm-eaten, there always remains a woody wall, often very thin, it is true, between two adjoining tubes.
The very existence of the adult teredos seems dependent upon the wood. Withdrawn from their galleries and placed in sea-water, they could be kept alive by Kater scarcely more than three or four days. Left in the wood, but taken out of sea-water, they would die within twenty-four hours. Deprived at the same time of contact with wood and sea-water, they perished at the end of one or two hours. In damp wood, that is, wood soaked with salt-water, their existence is prolonged somewhat. Wood and sea-water are, then, both necessary. If these two conditions of existence are furnished them, one can, Kater assures us, keep them alive during several months.
The teredo does not always remain in peaceable enjoyment of the home he has constructed, and the nourishment the water brings to him. 
Fig. 13. He finds himself exposed to the attacks of an enemy, of an annelide to which the late M. W. de Haan has given the name of Lycoris fucata (Fig. 13). In our day, as well as at former epochs, this annelide is constantly found wherever the teredo exists. His eggs and embryos are met with in the midst of those of that mollusk.
Kater has remarked that the adult annelide, leaving the muddy bottom, where he has hibernated, and in which the piles are driven, climbs along the surface of the wood toward the opening made by the teredo; there he sucks away the life and substance of his victim; then, slightly enlarging the aperture, he penetrates and lodges in place of the teredo. Later the annelide reappears and seeks for new prey. All the early writers on this subject state that they have found this annelide in wood at the same time with the teredo. It is remarkable that a Fig. 13 similar annelide, and perhaps the same, has been found in the cavities hollowed out in stone by the pholades.
It is important that it should be generally understood that this annelide is not only harmless, but renders the greatest service in devouring the wood-destroyer. It is a narrow annelide, ten to fifteen centimetres long, provided on his sides with a great number of small feet terminated with a point and garnished with hairs and showing in front a pair of strong upper jaws, horny and sharp, and lower jaws bent backward in form of hooks and carried outside by the aid of the lower lip, which is developed somewhat like the finger of a glove turned backward. Behind the head are four pairs of tubular-formed gills. With these weapons the annelide pursues and devours the teredo. The observations of Kater teach us that he is generally found in the empty galleries with the remains of the teredo; sometimes even he is seen as if clothed with the integuments of the teredo, while he is occupied in ransacking his intestines. Once Kater had the rare
