ACTINIARIA 



159 



v/ere developed, on the 

 other side two mesen- 

 teries of the 4th order 

 were lacking. In the 

 specimen from Ikamiut 

 the number was 55 (6 

 + 6 + 12 + 24 + 7 

 — compare the table) . 

 The arrangement of the 

 mesenteries thus seems 

 commonly to be deca- 

 merous, though it may 



happen to be hexame- Fig. 165 



rous. All mesenteries were perfect in the lar- 

 ger specimens, in the smaller specimens the last 

 cycle was not connected with the actinopharynx . 

 The number of mesenteries seems sometimes 

 to he a little smaller than that of the tentac- 

 les, which indicates that also here the mesen- 

 teries grow from the basis upwards, a rule, 

 which perhaps holds good for all Cribrinids. 

 The longitudinal muscles of the mesenteries 

 recall those of Urticina, and the pennons appear 

 as bands, a little but deeply folded. The parie- 

 tobasilar muscles are well developed, though not 

 as strong as in Urticina. The uppermost part is 



Fig. 168 



Fig. 169 



Fig. 167 



Textfigs. 165 — 169. Cribrinopsis siniilis. 



Transverse sections of sphincters (figs. 165, 166), of tentacles (figs. 167 



— 168 and oral disc (fig. 169). (Figs. 165, 167, spec, from Finmark; fig. 



166 spec, from Kola, Chewanna; fig. 169 spec, from Corea strait). 



rather narrow, and the muscles end before reaching the region of the sphincter. The basilar muscles are well 

 developed and discoverable to the naked eye. Oral stomata are present, sometimes also marginal stomata, 

 the latter, however, occur anytliing but regularly. All mesenteries are fertile, only on the directive mesen- 

 teries they are often lacking (compare the table p. i6o). The species is dioecious. 



Remarks. In this specimen I have never found any embryos in the coelenteric cavity. The most 

 closely examined specimens were however male. A specimen was a double animal, each specimen had two 

 pairs of directive mesenteries symmetrically arranged, perpendictdarly to the div-iding plane. 



The small fragments of the oral disc with tentacles, which Pax 1915 has determined as Actinostola 

 abyssorum, certainly do not belong to this species but to Cribrinopsis similis. I have namely examined such 

 tentacles taken in the Kola fiord (The Russian biological station) and labelled Zoanthus sp., and they were 

 tentacles of Cribrinopsis (PI. 3 fig. 7). The exterior aspect and the arrangement of the muscles are about 

 the same in both species, but the size and the structure of the nematocysts are very different. I have often 

 found such tom-off tentacles in Cribrinopsis from different locahties. 



