jQ ACTINIARIA 



(textfig. 4), mucus-cells are here also rather common, though rarer in the apex of the tentacles. 

 The mesogloea is thick, irregularly and grossly folded and of the same structure as in the column. The 

 endoderm is thinner than the other layers, the endodermal muscles weak. The oral disc is built as the 

 proximal parts of the tentacles, the elevations are, however, not as densely packed. The radial muscles 

 are a little stronger than the longitudinal muscles of the tentacles, and the mesogloea not as mucli 

 folded as there. 



The ectoderm of the actinopharynx makes several folds (compare above), supported by thick balks 

 of the mesogloea (textfig. j). In addition to numerous supporting cells mucus-cells are rather commonly 

 found in the ectoderm of the actinopharynx, but granular gland-cells very rarely — in maceration-prepara- 

 tions I have only observed few of these latter — furthermore stinging capsules, partly some uncommonly large 

 with strongly twisted thread of the same appearance as those in the tentacles, but a little shorter (53 — -60 

 X 13 — 17 n), partl}^ smaller ones, almost equally wide and with distinct basal part to the spiral thread (24 

 — 31 X 5 — 6 /i. Very seldom I have observed still larger ones of the same kind (46 X 5 ju) ; I have also found 

 stinging capsules in different stages of development (compare above). The nerve-layer and the longitudinal 

 muscles are ver>' weak, the mesogloea in the longitudinal ridges thick, and endoderm of the same appear- 

 ance as in the column. No differentiated siphonoglyphes. 



The number of mesenteries in the sectionised specimen from Sunde was 24, of which 6 pairs were 

 perfect, and of these 2 pairs of directives. The twelve mesenteries of the second cycle were regularly deve- 

 loped. They are thin and rise a little out of the column, only in the distal part they are stronger. Daniels- 

 sen says that there are 16 pairs of perfect and 16 pairs of imperfect mesenteries in the type-specimen. This 

 is, a priori, rather unlikely as the animal liad only 38 tentacles. Danielssen is certainly erring here as so 

 many times before. Nevertheless a third imperfect cycle might be present as well in the type-specimen as 

 in the second specimen from Sunde, in as much as more than 24 tentacles occur in both specimens. The 

 muscles of the mesenteries are very weak. The longitudinal muscles are attached to large folds of the meso- 

 gloea, (textfig. i), the parieto-basilar nuiscles are not folded, and basilar muscles lacking. The mesogloea 

 is thick in the upper part, tliin in the lower one, and only at the insertions of the mesenteries it is thickened. 

 The endoderm is rather high witli numerous nmcus-cells. 



The filaments of the mesenteries are simple, without ciliated lobes, and join only on the mesenteries 

 of the first cycle. They enter into the ridges of the actinopharynx without any direct limit (textfig. i), their 

 structure even much corresponding to that of the actinopharynx. They are very meandiian and of con- 

 siderable diameter. The gland-cells are rather rare, especially the nmcus-cells: the supporting cells nume- 

 rous, in sections with densely packed nuclei as in the ectoderm of the actinopharynx. The stinging capsules 

 are like those of the actinopharynx. The larger ones with twisted thread are rather rare and 41 — 62 fi long 

 and about 17 fi broad. Also of these latter I have observed stages of development. They are of variable size 

 and show the same structure as the stinging capsules in the apex of the tentacles. The tliinner capsules of 

 equal width are also rather rare and 24 — 31 /i long and about 7 ^ broad. Besides, I have seen some smaller 

 capsules of the same kind (17 — 19 x 4 //). In transversal sections the mesogloea shows a T-like appearance. 

 No endodermal limit-streak is found. 



