ACTINIARIA 



Colour: transparent yellowish- white, the proximal part with paler longitudinal lines (Fabricius). 



Dimensions: Length in preserved state unto 2,8 cm, breadth 0,25 cm. Length of the tentacles 

 about 0,25 cm. 



Occurrence: West-Greenland. Godhavn (Olrik), Ritenbenk (Andersen), Egedesminde (Trau- 



stedt, Olrik). 



Greenland without distinct locality (Hoi boll). On stones or shells at the shore, 

 also on sand (Fabricius). 



Further distribution: Shetland Islands (Fleming) (PPerhaps not this species). 



Exterior aspect: In extended state the body is expanded and cylindrical; in very contracted 

 state often broader in the proximal and distal ends. (PI. i, figs. 6, 7). Distinct pedal disc absent. It is true 

 that the proximal end of some of the examined species is flattened disc-like, but a distinct outline between 

 the most proximal part and the other part of the body is never to be observed. The proximal part is mostly 

 a little involved in the preserved specimens, but never swollen as a physa generally is. The column is smooth, 

 without papillae, divisible into two from each other very little differentiated parts, a longer scapus and a 

 shorter capitulum ; sometimes these regions seem to be separated from each other by a fold, recalling a fossa, 

 which is probably due to the contraction of the body. The scapus seems to be able to generate a thin mem- 

 brane which, however, may be a mucus-secretion. According to Fabricius the tentacles are 18 in number; 

 in 6 species, examined by myself, the number varied from 24 to 26. The tentacles, arranged in three cycles, 

 may be perfectly covered by the column; they are short, conical, not thickened in the apices and almost 

 all of about equal length, the outer tentacles are only a little shorter than the inner ones. The oral disc is 

 inconsiderable, with shallow, radial 'furrows. The actinopharynx is short, in the preserved specimens folded 

 and supplied with two weak siphonoglypb.es devoid of aboral prolongations. 



Anatomical description: The ectoderm of the "scapus" is very high and provided with nume- 

 rous mucus-cells and very sparse nematocysts (14 17 X 2 3 // in size). The ectoderm of the capitulum 

 differs from that of the scapus only in this respect that the mucus-cells are very sparse here. The mesogloea 

 of the column is thin and fibrillated. The endodermal circular muscles are a little stronger in the above- 

 named fold, but not forming any distinct sphincter there. The longitudinal muscles of the tentacles are weak, 

 the spirocysts of the tentacles are very numerous and of variable length, to about 22 X 3 /j. in size. The typi- 

 cal nematocysts are sparse and of the same length as in the column. The ectoderm of the actinopharynx 

 contains very numerous mucus-cells and numerous nematocysts with distinct basal part to the spiral thread. 

 They are widened in the basal end and 1722 X 45 n in size. The wall of the nematocysts in the ten- 

 tacles and in the actinopharynx is comparatively thin. In the siphonoglyphes the mucus-cells are very sparse 

 and the nematocysts absent or very sparse. 



The mesenteries are hexamerously arranged, in three cycles. Of these cycles the latter is more or less 

 perfect and only present in the distal part of the body. Thus the mesenteries of the third cycle of a specimen 

 were developed in the dorso-lateral and the lateral exocoels, but not in the ventro-lateral exocoels. Besides 

 this, the mesenteries of the third cycle end at a different level, even the mesenteries of one pair. Only the 

 first 6 pairs are perfect and provided with pennons. Judging by the unequal size of the filaments the ventral 



