176 



ACTINIARIA 



Occurrence: Arctic sea of Sibiria. 20 E. off Cape Jakan 12 fms. Sand and clay with stones 



(Vega-Exp.), 677' N. I7324' W. 9 15 fms. mud and stones 

 (Vega-Exp.), 2 miles N. of the winter station of the Vega 

 12 fms. sand (Vega-Exp.). 



Exterior aspect. The column was in contracted state generally conical, its length was often twice 

 its breadth; the single specimen with extended tentacles was elongated, cylindrical. The pedal disc was 

 as a rule a little involved and radially sulcated. The column was quite smooth in some expanded specimens, 

 in others furnished with longitudinal and transversal ridges, and devoid of sucking warts, acrorhagi and 

 pseudoacrorhagi. Its ectoderm is furnished with a weak cuticle, sometimes a little incrusted, and which 

 seems easily deciduous (compare below). In three specimens (from Cape Jakan) there are brood-rooms devel- 

 oped in the lower part of the column (compare Carlgren 1901), in the other specimens, among which there 

 were some females, no brood-rooms appear. The fossa is distinct. The tentacles were short, strongly contracted 

 and conical, about as long as broad, in one specimen more elongated, the outer tentacles a little shorter 

 than the inner ones. Their surface was in preserved state smooth or weakly sulcated. They were hexamer- 

 ously arranged, and the number in the examined species variates between 35 and 47 (35, 36, 41, 41, 43, 43, 

 44, 45, 47). The number of the tentacles was, as a rule, smaller than that of the mesenteries, in other words, 

 the mesenteries grow forth from below upwards. The actinopharynx was long and furnished with about 

 24 longitudinal furrows and ridges. The 2 symmetrically placed siphonoglyphes were broad, in the upper 

 part with 2 distinct gonidial tubercles, aborally a little prolongated. 



Anatomical description. The ectoderm of the column is high and contains numerous nemato- 

 cysts like that of the tentacles and the actinopharynx. The nematocysts of the column are longer and a little 

 broader than those of the tentacles, as the following table shows. 



The homogeneous gland-cells of the column are very numerous, the granulous gland-cells fewer. 

 The ectoderm of the column is furnished with a weak, easily deciduous cuticle. In some specimens it is lost, 

 in the type-specimens there were fragment of a cuticle incrusted with foreign bodies; the cuticle appears 

 most distinctly in the brood-rooms, from where it was not easily rubbed off. The mesogloea is rather 

 thick and contains small protoplasma-poor cells. The endodermal circular muscles were very well-developed 

 and the folds of the muscle layer ramificated. The sphincter was strong, of palmate type; in one examined 



