ACTINIARIA 241 



is not unlikely, as both species are very nearly related to each other. In the ectoderm of the actinopharynx 

 I have found only tjqDical nematocysts, 22 — 30 X 2 — 2,5 /« in size. 



The arrangement of the mesenteries agrees very well with that of Si. coccinea, I have, however, not 

 found anj' more than 16 perfect pairs in the five specimens which I have examined more closely. Of these 16 pairs 

 four are weaker than the other pairs and most frequently consist of one perfect and one imperfect mesenterj', 

 the former sterile as the other perfect mesenteries, the latter most often fertile. These weaker mesenteries 

 were placed symmetrically on both sides of the directive plane. If we indicate the mesenteries of the first 

 cycle with I, the stronger perfect mesenteries of the second cycle with 2 and the weaker of the same cycle 

 with 2j, the stronger and always perfect 2j mesenteries with a, the weaker with h, the arrangement of these 



dm 



mesenteries on both sides of the directive plane was the following I 2 2i I 2 2^ I 2 (I). In a primary dorso 



ab a b 



lateral (?) exocoel thus no 2j-mesenteries are developed. The mesenteries besides follow the Actinosiola-TVile in 

 their development. A specimen, the pedal disc of which was 1,8 cm broad, the height of the column 1,9 cm, 

 and the number of tentacles 95 in the region of the actinopharynx, shows the following arrangement of the 

 mesenteries. 0: unpaired mesentery in this region. 



dm dni 



143424342,3 I43424342i3 14342434 14342434 I 32^4342434 I 4342i4342434. 



00000 



The weakest mesenteries are in the vicinity of 2^. In the most proximal part of this specimen the 

 number of mesenteries was 171. Thus the number of mesenteries, in comparison with that of the tentacles, is 

 much smaller in this species than in St. coccinea. If we take the number of tentacles to be i in both species, 

 the number of mesenteries in the named ^o/an's-specimen is 1,8, in the more explicitly described specimen of 

 St. coccinea 4,76. As for the rest of the organisation it agrees with that of St. coccinea; I have, however, some- 

 times found a small marginal stoma. The longitudinal muscles of the mesenteries vary in appearance, prob- 

 ably according to their different state of contraction, they now recall those of 5^. coccinea (Carlgren 1893), 

 now those of St.(Cymhactis) selaginella (Stephenson 1918a), now they are more expanded over the whole 

 surface of the mesenteries; the longitudinal pennons, commonly provided with higher folds than in St. coccinea, 

 are however limited to the outer part of the mesenteries. 



The Ingolf-Expedilioii. V. 9. 3' 



