136 



ACTINIARIA 



mesogloea commonly is more thick, the meshes are more scattered, and larger and smaller meshes are in- 

 termingled. 



The ectoderm of the tentacles is high and contains rather numerous nematocysts, 19 24 ft long, 

 and very numerous spirocysts of variable size, from 17 X 2 ft to 29 X 3,5 fjt. The longitudinal muscles are 

 ectodermal and well developed in the proximal part, here forming palisade-shaped folds, in the distal part, 

 however, weaker. At the base the longitudinal muscles are a little stronger on the inner side than on the 

 outer one. The endoderm is high and extended in numerous off-shoots. 



The ectoderm of the oral disc contains nematocysts similar to those of the tentacles, their number 

 is, however, considerably smaller. The radial muscles are strong and almost exclusively ectodermal, still 

 there are sparse meshes enclosed in the mesogloea. The folds are numerous and higher than the un- 

 folded part of the mesogloea. The ectoderm and the mesogloea are much thinner at the insertions of the 

 mesenteries than in the intermediate parts. 



The actinopharynx is folded. The ectoderm contains very numerous typical nematocysts, 19 22 

 X 2 ft in size, besides these also sparse nematocysts with visible basal part to the spiral thread. The latter 

 are broader in the basal than in the distal end and 22 26 X 3,5 n in size. The gland-cells are numerous ; lon- 

 gitudinal muscles absent. The mesogloea is thicker than the ectoderm at the ridges, weaker in the furrows. 

 The siphonoglyphes are narrow, their ectoderm contains less numerous nematocysts and gland-cells than 

 the other part of the actinopharynx. 



The pairs of mesenteries are 12 of which two pairs of directives. 6 pairs are perfect and 6 imperfect. 

 The pairs of the first cycle are provided with large, longitudinal muscle-pennons which are, however, rather 

 short and mostly developed in the distal part. The larger part of these mesenteries is devoid of pennons and 

 the proximal part of the mesenteries therefore looks like thin lamellae. On the top of the lower part of the 

 actinopharynx the pennon is the most developed on the outside, the folds are high and rather richly rami- 

 ficated here (textfig. 156). In the reproductive region the pennon is, however, almost as much developed 

 on the inside as on the outside. As the outer lamellar part of the mesenteries issues from the middle part 

 of the pennon, which is thickened in the region of the actinopharynx as well as in the reproductive tract, 

 the pennon looks rather circumscribed in transverse-sections through the reproductive region (textfig. 157). 

 The folds amount to about 20 in number. The parietal muscles are not strong, the folds are few, low and 

 not transversely expanded, but radially elongated (textfig. 157). They are not expanded upon the column. 

 The muscles of the mesenteries of the second order (textfig. 158) have no pennons and are in transverse- 

 sections of about the same appearance as the parietal muscles of the first cycle. The filaments are well deve- 

 loped on the mesenteries of the first cycle. Whether such filaments appear also on the mesenteries of the 

 second cycle I cannot with certainty decide as my material was not in every respect well preserved, it seems, 

 however, in certain cases as if also these mesenteries might be provided with very weak filaments. The cili- 

 ated streaks are of typical appearance, their mesogloea contains few cells. Acontia are present, but I cannot 

 decide where they are attached. I have observed them in transverse-sections, they are typical and provided 

 with large nematocysts. The reproductive organs are developed in the proximal part of the pennons of the 

 mesenteries of the first cycle. In two examined specimens they were ovaria. I have not found any reproductive 



