ZOANTHARIA 17 



very instructive figure of a transverse section in PL 59, fig. 6. It must be observed however, that in 

 ray specimens the strands of the mesoglcea, separating the different parts of the ectoderm from each 

 other, do not always lie so closely as in this figure. 



As mentioned by Had don and Shackleton the sphincter is not strongly developed, espec- 

 ially if the size of the polyps is taken into consideration. In the distal part of the sphincter, however, 

 the fibres occupy almost the whole breadth of the mesogkea, the lower third part of the sphincter 

 being inconsiderable. Had don and Shackleton state that "no cavities are visible, the fibres 

 being completely embedded in the substance of the mesoglcea." This is not the case in my specimens. 

 In the proximal part, where the muscle-meshes (in transverse sections through the sphincter) are small, 

 it may be possible that there sometimes are no cavities, in the distal part on the other hand the 

 muscle-meshes are large and as usual extend in a transverse direction. The parts of the mesoglcea 

 lying between the muscle-groups are very small. The sphincter is thus fairly strong in this regard. 



The ectoderm of the tentacles is high, the mesoglcea on the other hand is thin as also the 

 layer of longitudinal muscles. In the ectoderm very numerous spirocysts are found. Whether thick- 

 walled nematocysts occur is uncertain, but if present they are very scarce. 



The ectoderm of the oesophagus is fairly high and provided with numerous, thick-walled 

 nematocysts (length 23 — 29 /i, generally about 24—26 fi). The mesoglcea is fairly thin. In the 

 siphonoglyphe the ectoderm is considerably thicker than in the oesophagus, with the condition reversed 

 as regards the mesoglcea. The mesoglcea in the siphonoglyphe is almost homogeneous, as cells and 

 cell-islets only occur very seldom. 



The number of mesenteries is greater than in any other northern Zoantharia. In a small 

 polyp I counted namely 64 mesenteries, 17 macro and 15 micro on each side, in a large one 80 

 mesenteries. The macro-mesenteries are in the oesophageal region fairly thick, owing to the fact, 

 that the mesoglcea is well-developed here, whereas it becomes thinner below the oesophagus. The 

 longitudinal muscles are not strong and the muscular plaits few. The parieto-basilar muscles are very 

 weak and narrow. None of these muscles are expanded in the body-wall. The micro-mesenteries 

 are very weak — the weakest I have ever seen — and do not reach above the entoderm of the 

 body-wall. 



The filaments have the usual structure. They contain nematocysts with greatly twisted thread, 

 but not in great number. They are oval and fairly small (length 19—25,0, breadth 10 — 12 /*). Further, 

 they contain fairly many thick-walled, rather transparent nematocysts with distinct spiral thread and 

 broader at the one end, with varying length (19—24 — 26—31^, breadth 6 — 7 /*) and also some thick- 

 walled, narrow, typical nematocysts (length about 26^). 



The species is dioecious. 



The carciiio'ciiiiu. The cceneiiehyme and the canal-system have not been examined by H addon 

 and Shackleton. The outer layer of the ectoderm had fallen off. The mesoglcea sends out a 

 number of fine outshoots, the presence of which indicates that the ectoderm is also discontinuous 

 here. On the inner side the ectoderm is thin and discontinuous with a well-developed cuticle. On 

 the outer side of the carciuceeium the mesoglcea is very thick, on the inner side it is thin. The 

 entodermal canal-system (c, text-fig. 3, p. 13) thus lies quite close to the inner side of the ccenenchyme. 



The Ingolf-Expedition. V. 4. 3 



