ZOANTHARIA 



51 



The ectoderm of the oesophagus has the usual structure. Nematocysts probably also occur 

 there, but as parts of the filaments are connected with the ectoderm of the oesophagus the macerated 

 preparation has given no certain information regarding the occurrence and appearance of the nema- 

 tocysts. The mesoglcea is thin and considerably weaker than in the siphonoglyphe. 



Mesenteries. Of 3 specimens sectioned only one was so well fixed that I could determine the 

 number of mesenteries. This polyp has 32 typically arranged mesenteries. The mesenteries are thin, 

 the longitudinal as well as the parieto-basilar musculature weak. These muscles extend a long way 

 onto the body-wall. The micro-mesenteries are fairly well-developed even below the oesophagus. 



The filaments have the usual structure. The nematocysts are partly large, uniformly broad capsules 

 with greatly twisted thread (length 31— 43 /i, breadth 12/1), partly smaller often somewhat curved (length 

 about 15U, breadth 7^). The latter are common. Further, the filaments contain fairly many, thick- 

 walled capsules with distinct basal part to the spiral thread and somewhat broader at the one end 

 (length 22 — 24//, breadth 7 n). The species is dioecious. The best preserved specimen had well-developed 

 testes 011 the macro-mesenteries. 



Systematic remarks. In some respects this species resembles /. multinsulosus , from which 

 it differs however in a number of features. In /. magninsulosus the large cell-islets (the lacunae) in 

 the mesoglcea of the body-wall are, for example, more numerous and larger than in /. multinsulosus 

 (cf. above), in this species the incrustation consists of foraminifera, in /. magninsulosus of sand-grains, 

 and in this the ectoderm is less pigmented than there. In I. magninsulosus the number of mesenteries 

 is 32, in /. multinsulosus 38 — 40. Also the large nematocysts are somewhat shorter and especially 

 narrower here than in /. multinsulosus, though otherwise they resemble each other with regard to the 

 nematocysts. 



Isozoanthus multinsulosus u. sp. 



PI. 1, fig. 18. PI. 6, fig. 3. 



Occurrence: 64°i5'N., i4°22'W. 68 m. Bott. temp. 7"07°. Ingolf Ex. St. 51. 1 colony. 

 65°43'N., i4°34'W. 90 m Bott. temp. 7 . Ingolf Ex. St. 6. 1 colony. 



Dimensions. The polyps were strongly contracted. Largest polyp about 0-45 cm. broad and 

 1 cm. high. 



Colour. The polyps are black owing to the incrustation of black sand-grains. It is probable, 

 however, that the polyps are dark in themselves as the ectoderm and especially the entoderm are 

 darkly pigmented. 



External appearance. One of the colonies consisting of 4 polyps was attached to a stone, 

 the other colony with 3 polyps to a Dentalium-tube. The greatly contracted polyps were connected 

 with each other by a very thin, spread ccenenchyme from which the polyps emerge, sometimes at 

 smaller, sometimes larger intervals. The polyps are short, the upper margin of the polyps retracted 

 in the distal end, not truncate but rounded. Capitular furrows present but so indistinct that I am 

 unable to state their number. The tentacles have the usual structure. The oesophagus is short, 

 siphonoglyphe deep, hyposulcus distinct. 



r 



