On the "Glass-Rope" Hyalonema. 91 



former, as a still thinner membrane, with a somewhat stellate 

 arrangement of its substance, can sometimes be detected 

 beneath it, and spreading along the large spicule beyond the 

 portion incrusted by the zoophyte. This, the most delicate of 

 all the investments, very probably consists of a dried- up layer 

 of sarcodic sponge matter. 



I have lately dissected carefully the species or variety of 

 Palythoa, which gives its peculiar character to Brandt's Hya- 

 lochceta Possleti. In this species the projecting polyps are 

 cylindrical, and in some cases about a line in length. In their 

 retracted state, they show a small round opening in the centre 

 of a mammillary projection, the opening surrounded by about 

 twenty obscure radiating lines. When softened by being 

 steeped in dilute acetic acid the polyps become quite plump, 

 and are almost as easily examined as if they were fresh. The 

 external body- wall consists as usual of two layers, of which the 

 outer is thickly coated with imbedded grains of sand. In the 

 specimen I last examined, I could not detect in this layer 

 a single characteristic spicule of Hyalonema; fragments 

 only of linear needles were mixed here and there with the 

 sand. In other specimens, however, I have found the surface 

 crowded with Hyalonema spicules ; but I am confident that in 

 these cases they were embedded simply as grains of sand, or 

 any other foreign bodies might have been. The peristomial 

 space contains a crown of at least sixty tentacles, in three 

 alternating rows, those of the outer row the larger. The ten- 

 tacles are short and conical, with the peculiar curve which is 

 characteristic of ZoarUhus and its allies ; rather large oval 

 thread cells are scattered sparingly in their walls.* The 

 digestive sac is fluted and corrugated, and its upper portion 

 only is attached to the body wall by about twenty membranous 

 mesenteries. There is no trace of spicules, either silicious or 

 calcareous, in the inner layer of the body wall, in the wall of the 

 stomach, or in the mesenteries. 



There seems to me to be no character whatever to separate 

 this zoophyte from the well-known zoantharian genus Paly- 

 thoa, to which, following Professor Schultze, I have already 

 referred it. I have not yet had time to examine many 

 specimens with due care, but my present impression is that we 

 are acquainted with three species of Palythoa incrusting the 

 coils of two species of Hyalonema — 1. the Palythoa with 

 round, depressed, irregularly-arranged polyps, parasitical upon 

 most of the specimens of Hyalonema kieholdi from Japan ; 



* The crenated tentacle figured by Schultze (Taf. 5, Fig. 4) is riot that of 

 Palythoa, as stated by Dr. Gray (dnn. and Mag., Nat. Hist, Oct. 1808), but is a 

 tentacle of the minute Alcyonarian parasite, which Professor Schultze detected 

 within the pores and passages of the sponge. 



