ZOANTHARIA 



53 



External appearance. Small colonies consisting of some polyps connected by a thin, fairly 

 extensive coenenchyme attached to small stones, mollusc-shells or worm-tubes. The polyps are cylindrical 

 and sometimes, owing to contraction, a little thicker in the distal part, and longer than broad. In the 

 retracted state the distal part is almost truncate with a depression in the middle. Capitular furrows 

 present but very indistinct, in the best preserved specimen 20 were observed. The polyps as well as 

 the coenenchyme were incrusted with sand, now and then with sponge-needles; near the ectoderm 

 mud-particles are fixed. The incrustation is not very strong and restricted to the ectoderm and 

 especially the outer part of the mesogloea. 



The oesophagus is short with a very distinct deep siphonoglyphe and well-developed hyposulcus, 

 which is somewhat longer than the oesophagus. 



Anatomical description. The ectoderm of the body-wall is moderately developed, yet several 

 times thinner than the mesogloea. In the proximal part of the body-wall large nematocysts with coiled 

 thread are found, sometimes sparsely (specimens from the Ingolf Expedition), sometimes more commonly 

 (length 31 36^, breadth 12 14 fi). In the Finmarken specimen some smaller capsules of the same 

 appearance as the smaller egg-shaped capsules of the filaments are also found. The mesogloea is thick 

 and contains numerous cells with long outshoots, sometimes running in the direction from ecto- to 

 entoderm (PI. 6, fig. 6) and sometimes even more irregularly arranged. Further, there is a sparse 

 occurrence of small cell-islets and large cells. The latter sometimes fuse together to form (ectodermal ?) 

 lacunae. The large cell-islets lie often near the insertions of the mesenteries. As the cell-islets fuse 

 together forming lacunae, it may sometimes on certain parts of the proximal part of the polyps look 

 as if traces of an encircling sinus might be present. As the cell-islets lie fairly irregularly and are 

 generally separated from each other by large portions of mesogloea, especially in the distal end of the 

 polyp, the lacunae cannot however be considered as an encircling sinus. The entoderm is thinner 

 than the ectoderm. 



The sphincter resembles that of /. arborescens and forms large folds. 



The ectoderm of the tentacles has the usual structure and contains numerous spirocysts and 

 fairly thick-walled uematocysts (length 19 2O//). Besides there are very sparsely large capsules of 

 the same kind as in the ectoderm of the body-wall. In the specimen from Finmarken I observed 

 small capsules with coiled thread (length 19^, breadth 7/4 The mesoglcea of the tentacles is incrusted 

 though only inconsiderably. 



The ectoderm ^of the oesophagus is high and contains fairly many thick-walled nematocysts 

 (length 17 22//). Further, there also occur, though only very sparsely, some larger or smaller capsules 

 with coiled thread of the same appearance as in the filaments. The ectoderm of the siphonoglyphe is 

 as usual considerably lower than in the oesophagus, whereas with regard to the mesogloea the 

 condition here is reversed. 



In the two specimens taking during the Ingolf Expedition the number of mesenteries was 40 

 and 38; the first of them had the mesenteries arranged typically, whereas the second had a pair of 

 mesenteries less on the one side than on the other. Of the specimens from Finmarken one had 46 

 mesenteries, 13 macro and n micro on one side and 12 macro and 10 micro on the other. Another 

 specimen probably had 44 mesenteries -- n being observed in one fourth part of the polyp. 



