ACTINIARIA 



between the insertions of the mesenteries, in the other parts the mesogloea is more equally thick. The nema- 

 tocysts of the tentacles reach a size of 15 22 X 2,5 ;i, the spirocysts are about 12 19 p long. The high 

 ectoderm in the actinopharynx-ridges contains nematocysts, 16 24x2,5 3 p in size. The mesogloea of the 

 actinopharynx is thin, still a little thickened in the ridges. 



The longitudinal pennons of the mesenteries are rather well developed, with about 13 to 15 folds 

 in the regions of the ciliated streaks and of the reproductive organs. The folds are in the inner and especi- 

 ally in the outer parts very little ramificated and high, while in the middle of the pennons they are short 

 and not branched (textfig. 81). The outer lamellar part of the mesenteries issues from the pennons rather 

 close by the outside. The parietal muscles are not strong, with a few, short, broad folds, supported by thick- 

 enings of the mesogloea; on the other hand they are considerably expanded on the column (textfig. 80). The 

 filaments of the mesenteries were badly preserved, so that I cannot give any information of their appear- 

 ance. The animal is dioecious. 



Remarks: This species is rather interesting, as in some respects, concerning the arrangement of 

 the nematocysts, it may be regarded as a previous stadium of the genus Edwardsia. If we imagine the nema- 

 tocysts and their mother-cells in the column of M. polaris to be wholly enclosed in the mesogloea and the 

 supporting cells reduced, we have a nemathybome. The genus Edwardsia cannot, however, directly descend 

 from Milnc-Edwardsia, because the arrangement of the tentacles in Edwardsia, compared with that of Milne- 

 Edwardsia, shows that both genera are developed, each in its own direction. 



Milne-Edwardsia nathorstii n. sp. 



Diagnosis: Proximal end rounded without distinct physa. Scapus with a well developed cuticle. 

 Nematocysts of the scapus-ectoderm concentrated in small groups containing only some few capsules, 29 

 -36 X 3,5 5 n in size. Tentacles 12. Their ectoderm with very close spirocysts of variable size, the greatest 

 spirocysts reach a size of 34 36 X 5 ;i. Nematocysts in the ectoderm of the tentacles not numerous, 31 

 3 X 3,5 5 fjt. Nematocysts of the actinopharynx 34 36 X 5 //. Longitudinal muscle-pennons of the mesen- 

 teries in transverse-sections through the upper part of the reproductive region with some few, about 10, 

 low folds, supplied with short, secondary folds. The lamellar outer parts of the mesenteries issue not far 

 from the middle of the pennons. Parietal muscles not strong, with rather few folds, but they are consider- 

 ably expanded on the column, where they have comparatively high folds. 



Colour in alcohol: Scapus dirtily-yellow. 



Dimensions in contracted state: Length of the column about i cm, breadth 0,15 cm. 



Occurrence: East-Greenland. Scoresby Sound, Hurry's Inlet, 7O43' N. 22 2g' W. 30 m mud 

 (Sw. Greenl. Exp. 1899, N - 455. 456) 9 S P- 



N. of Spitzbergen 8i2o' N. 2o3o' E. 1000 m (Roemer & Schaudinn, 1898, St. 

 41) i sp. 



Exterior aspect: As all specimens were contracted, with the distal part involved, and only of 

 small size, I cannot give any complete information of the exterior of the species. The description is made 

 after an examination of the specimens from Greenland. 



9* 



