l82 



ACTINIARIA 



Colour? 



Dimensions in contracted state: length and breadth about 2,2 cm. 



Occurrence: 20' E. off Cape Jakan 12 fms. Sand and clay with stones (Vega-Exp.) i sp. Together 

 with E. marsupialis. 



Exterior aspect. The pedal disc is well developed and the column smooth, without spots. The 

 fossa is deep, the tentacles from conical to cylindrical, smooth and rather thick, in number probably as many 

 as the mesenteries. Only about 20 tentacles were, however, perspicuous, but as I have observed some involved 

 tentacles in the weakest compartments, I think that the number of tentacles and mesenteries is the same. 

 Concerning the appearance of the actinopharynx I cannot give any perfect informations, as it was very 

 contracted and badly preserved, and partly in a mess with the reproductive organs. It is, however, distinctly 

 longitudinally sulcated. 



Anatomical description: The ectoderm of the column is high and contains numerous mucus- 

 cells and nematocysts (size compare the diag- 

 nosis). The mesogloea is thick, and the en- 

 dodermal circular muscles much weaker than 

 those of the former species. The sphincter is 

 of a decidedly palmate type (textfig. 182), on 

 transverse sections round and well-developed. 

 The ectoderm of the tentacles is high, the 

 nematocysts and the spirocysts (compare the 

 diagnosis) numerous. Their longitudinal musc- 

 les (textfig. 181) are strong, and recall those 

 of Cribrina spetsbergcnsis, but are ectodermal ; 

 there is but rarely a mesogloeal mesh at the 

 base of the muscle folds. The radial muscles 

 of the oral disc are weaker, especially at the 

 insertions of the mesenteries. Here the muscles 

 seem to show a tendency to become mesogloeal, whereas they are ectodermal between the mesenteries. The 

 nematocysts of the actinopharynx are numerous (size compare above) . The ectoderm and also the endoderm 

 of the siphonoglyphes are very high, an ectodermal longitudinal muscle layer is present. 



The mesenteries are hexamerously arranged, though even at the origin of the second cycle the devel- 

 opment of certain pairs of mesenteries is checked. If we mark with figures the different cycles of mesenteries 

 and begin with the one directive pair (dm), the arrangement is the following. 



dm dm 



13213211123123== 14 pairs (6 + 4 + 4 ). 



The pairs thus were equally checked on both sides of the directive plane. In two primary exocoels, 

 one on each side of the one directive pair, there are no mesenteries of the second and third cycles, and in 

 the other primary exocoels the mesenteries of the third cycle are present only in the exocoels of the second 



Fig. 181 



Fig. 182 



Textfigs. 181, 182. Epiactis incerta. 



Transverse sections of part of a tentacle (fig. 181) 



and of the sphincter (fig. 182). 



