ACTINIARIA 12 - 



portance. Danielssen states that the circular muscles of the column of Cactosoma are mesogloeal, this is, 

 however, wrong; these muscles are, as usual, ectodermal, only the sphincter is mesogloeal, and this part 

 has not been examined by Danielssen the distal part of the type-specimen not having been sectionized 

 by him. The ectoderm of the tentacles is very high and contains very numerous spirocysts of variable size, 

 from about 24 X almost 2 to 36 x 2,5 ft and sparser nematocysts 14 22 x 2 2,5 (3,5) p in size. The ecto- 

 dermal longitudinal muscles of the tentacles are well developed, forming high folds, palisade-shaped and a 

 little ramificated. The mesogloea and the endoderm of the tentacles are thinner than the ectoderm. The radial 

 muscles of the oral disc are rather strong, and appear in transverse-sections as closely packed lamellae. The 

 ectoderm of the actinopharynx is rather high and provided with numerous granular gland-cells and rather 

 common, typical nematocysts (about 14 20 ft long) ; besides these, there are also nematocysts here with 

 visible basal part to the spiral thread (22 33 x 4,5 5 n in size). I have not examined the siphonoglyphe 

 more closely, but it looks as if it is weakly developed. I have examined the stinging capsules in Phellia crassa 

 as well as in Cactosoma and in the specimen from the Michael Sars-Expedition. They agree well in size; in 

 Phellia crassa I have not observed any nematocysts with visible basal part to the spiral thread. 



The mesenteries are arranged in two cycles and are also 24 in number, 6 pairs of perfect and fertile 

 and 6 pairs of imperfect and sterile mesenteries. The former have pennons, the latter not. The folds of the 

 muscle-pennons are very strong and high, especially in the tract of the actinopharynx (fig. 9, 1902) ; in the 

 reproductive region they are from 20 to 30 in number, commonly of equal height and somewhat richly rami- 

 ficated, particularly in the outer and the inner parts. The outer lamellar part of the mesenteries is attached 

 to the pennon close by its outer edge (fig. 150). The parietal muscles are strong, in transverse-sections elon- 

 gated, that is, much expanded radially (textfig. 151 from the type-specimen of Cactosoma). The mesogloea 

 is rather strongly thickened in the tract of the parietal muscles ; from the main lamella issue numerous, but 

 not high folds which are more or less ramificated. The folds are of rather equal height, the highest folds 

 still being situated in the innermost part of the parietal muscles. More strongly contracted parietal muscles 

 appear more flattened. They are only a little or not at all prolonged on the column, so are also the muscles 

 of the imperfect mesenteries, the appearance of which very much recalls the parietal muscles of the perfect 

 mesenteries (textfig. 152 from the type specimen of Cactosoma). 



In my report (1902, p. 45) I have supposed that Phclliomorpha crassa has weak basilar muscles. 

 A closer examination proves that these muscles are nothing but the exterior part of the parietal muscles 

 which, where the physa-region begins, are more strongly curved than the inner parts of these muscles and 

 therefore, in transverse sections through the mesenteries in the region of the physa have been hit trans- 

 versely or obliquely, while the inner part of the parietal muscles are hit more longitudinally. If transverse- 

 sections of the Actiniaria seem to have very weak, not well marked basilar muscles, a control-examination 

 of these muscles ought to be made on surface preparations of the mesenteries, the ectoderm having been 

 pencilled off. On such preparations the arrangement of the muscles is namely more distinct than on single 

 sections. The perfect mesenteries have mesenterial filaments, the imperfect mesenteries none. The ciliated 

 streaks are of typical appearance, their mesogloea contains few cells. Danielssen declares that there are 

 acontia in Phellia crassa, I have not observed any such. Only the perfect mesenteries are fertile. The species 

 is dioecious. 



