Part II. — Stkhodactylince and Zoanthecc. 205 



folded backwardly and outwardly, so that in transverse sections through this region 

 its endoderm and ectoderm are cut through twice ; and, further, the ectoderm 

 appears to be continued radially for some distance along the mesenteries. The 

 mesenterial filaments are, however, simple throughout, that is, only the middle lobe 

 is present, the lateral lobes with the Flimmerstreifen not being developed. 



Although numerous polyps have been sectionized, it has been found impossible 

 to make out the complete arrangement of the mesenteries. In most ten mesenteries 

 are perfect, being united with the stomodseum at varying intervals. Nine perfect 

 mesenteries occurred in one example. No certain indications of imperfect mesen- 

 teries were afforded. The mesogloea of the mesenteries is swollen at its origin in 

 the column- wall and encloses cell-islets ; beyond the origin it thins rapidly. An 

 extremely weak parieto-basilar musculature occurs. The retractor muscle fibres of 

 the mesenteries are similarly very feeble, the mesogloea being slightly plaited to 

 give increased support ; the fibres appear to be strongest about the middle of the 

 width of the mesentery. The mesenterial endoderm is broad and crowded with 

 zooxanthellse ; it is more swollen below, and contains an abundance of small, 

 spherical, apparently non-nucleated bodies, which stain deeply. Pigment granules 

 are practically absent, but about the middle of transverse sections of mesenteries a 

 peculiar accumulation of fine, yellowish brown granules occurs on each face, very 

 limited in its radial extent. The endoderm throughout the polyps occasionally 

 contains large zooxanthellse-like bodies with a highly refractive cell-wall. No 

 gonads were indicated in any of the polyps sectionized. 



The species was trawled on only one occasion, February 10, 1898, at a depth 

 of 10—14 fathoms, on the Pedro Bank, Caribbean Sea, commensal with a silicious 

 sponge. 



In a list of the Actiniai-ia around Jamaica (1898ff), I identified the form as 

 the much debated Bergia catenularis, Duch. & Mich., its commensal habit and very 

 decided catenulariform appearance suggesting this species most forcibly. I am 

 now convinced, however, that the safest course is, for the present, to regard it as a 

 new species and await the possibility of discovering others which may approach the 

 older species more closely. Especially may this be the case in regard to the nature 

 of the coenenchyme connecting the individual polyp. From Duchassaing and 

 Michelotti's figure, B. catenularis appears to have this better developed than in the 

 present species, and more in the form of stolons, but I do not attach much impor- 

 tance to the statement that the connexions arise from the upper part of the polyps. 

 This is probably merely a result of the colonies being partly embedded in the 

 sponge, and P. monostichus affords indications of the same feature. There is little 

 doubt that the two species of Bergia will, when rediscovered and sectionized, be 

 found to belong to the genus Parazoanthus. 



TEASS. BOY. DUB. SOC, N.S. VOL. VII., PART VI. 2 G 



