REPOKT ON THE ACTINIARIA. 119 



attached close to the oesophageal groove, which is also ventral. Besides these there are 

 fifteen pairs of septa on either side (if the aggregate number of pairs of septa is increased 

 to thirty-three, there are sixteen on one side and fifteen on the other), which consist of 

 (1), a pair of septa adjoining the dorsal directive pair, and having the dorsal septum 

 larger than the ventral ; (2), thirteen pairs of septa situated towards the ventral aspect of 

 the body, and having the ventral septum larger than the dorsal ; and (3), a pair consisting 

 of two macrosepta and lying between the two above mentioned groups. The distinction 

 then between Epizoanthus parasiticus and Epizoanthus axinellce on the one hand and 

 the true Zoanthus on the other, is that in the latter the two systems are separated by 

 microsepta, in the former by macrosepta, so that a pair of septa is madeup of one septum 

 from either system. 



The remarks made by me on the septal canals and mesenteric filaments of Zoanthus 

 apply equally to Epizoanthus parasiticus. The reproductive organs were well developed, 

 and seemed to lie only on the macrosepta, and that without exception ; they were testes in 

 the specimen which I examined in transverse section. 



The individual animals of the Epizoanthus colony were united at the base by a 

 tolerably thick crust, in which numerous canals run from one polyp to another ; all the 

 canals extend with rejDeated anastomosis in one and the same layer of the coenenchyma. 

 Hence if we cut a colony through longitudinally, the coenenchyma is separated by the 

 vascular stratum into a broader external and a narrower internal layer ; the character of 

 the tissue is the same in both, except that the inner layer is without branched fibres. 

 The gastric spaces of all the polyps reach as far as the vascular stratum, in which 

 lies a very large canal surrounding the opening of the shell like a ring (PI. III. fig. 9). 



The hollow of the shell enclosed by the coenenchyma is lined by a chitinous 

 membrane, which lies firmly attached to the thin layer of the coenenchyma, and has a 

 structure of its own. Two lamellae are separated from one another by an interspace, 

 and are connected by perpendicular septa parallel to one another which divide the inter- 

 space into numerous tubes and smaller prismatic spaces. I leave it an open question 

 whether this chitinous membrane is the last remains of the Gasteropod shell or a cuticular 

 formation secreted by the superficial epithelium of the Epizoanthus. 



The mode of life of Epizoanthus parasiticus is the same as that of Epizoanthus 

 papillosus and Epizoanthus cancrisocius, the former of which was described by Gray in the 

 Proceedings of the Zoological Society, 1867, p. 237, the latter by Studer in the Monats- 

 berichten der Berliner Academic, Jahrg., 1878, p. 547. Both forms settle on Gasteropod 

 shells, occupied by a hermit crab, and completely absorb the calcareous parts of the shell. 

 The upper section of the wall oi Epizoanthus papillosus appears to be of the same nature 

 as that of Epizoanthus jximsiticus. I cbaw this inference from Gray's words in the 

 description given of the individual polyps, " The apex when expanded is flat, with close, 

 radiating white lines." It is therefore still a question whether these arc merely allied 



