The fact is no longer doubted by any one, that the long spicules form part of the sponge, and that the polyp establishes itself on a part of the colony. But science rarely advances by a single stride, and Max Schultze, like his predecessors, mistook the top of the
sponge for the bottom; Professor Loven has shown the true pose of the Hyalonema, and this he has effected by means of a small specimen from the Northern Sea.
Semper found a new Œga, to which he gave the specific name of Hirsuta, in an enlarged canal of the new Hyalonema of the Philippine Islands, which he dedicated to Mons. Schultze.
The Adriatic also produces a species of the same genus (Polythoa) which inhabits, like that of the Chinese Sea, a sponge to which the name of Axinella has been given. These Polythoæ are only found on the Axinellæ, says Osc. Schmidt, who has especially studied the sponges of this sea and of the Mediterranean. Professor Gill mentioned at the last meeting of the scientific congress at Portland (1873), a new Hyalonema found on the coast of North America by the fishery commission of the United States. A memoir on these sponges, interesting in a systematic point of view, is due to the pens of Herklots and of Marshall.
Fig. 1.—Ophiodendrum abietinum on Sertularia abietina.
We think that we ought to place among fixed messmates a very problematical organism which lives on Sertulariæ, especially on the Sertularia abietina, and which Strethill Wright has designated by the name of Corethria sertularia. Claparède has given to this singular animal the more expressive name of Ophiodendrum abietinum.
We have regularly found it on the Sertularia abietina at Ostend, every time that we have had an opportunity of observing these polyps immediately that they have been raised from the bottom of the sea. It is an organism whose affinities are not yet established.