ACTINIARIA 



211 



Genus Sicyonis R. Hertw. 



Diagnosis: Paractiidae with well developed, enlarged basal disc and from rather thick to thick, 

 cartilaginous, smooth column, which, in contracted state, is sometimes somewhat sulcated in the upper 

 part and here capable of involution. Sphincter weak or rather well developed. Tentacles short, the inner 

 considerably stronger than the outer ones, often more or less thickened on the outside of the base and in 

 that case with the longitudinal muscles stronger on the inner, weaker on the outer side or disappearing 

 at the base, only about half as numerous as the mesenteries. Longitudinal muscles of the tentacles and radial 

 muscles of the oral disc mesogloeal. 2 broad siphonoglyphes. The arrangement of the mesenteries is not as 

 regular as in Actinostola, variable, but with a strong tendency to a different development of the two mesen- 

 teries in the same pair. Often 16 pairs of perfect mesenteries, a variable number of pairs, in which one mesen- 

 tery is perfect, the other not. Mesenteries with no distinct longitudinal pennons. Parietobasilar and basilar 

 muscles well-developed. Mesenteries differentiated into stronger sterile mesenteries with well developed 

 filaments and into weaker fertile without filaments, the latter appear at the limbus and grow from here 

 in oral direction but do not reach the most distal part of the column. 



Among the species described below, Sicyonis tuberculata and ingolfi are nearly allied to the type- 

 species Sicyonis crassa. The agreement is so perfect in important characters, as f. inst. in the presence of 

 mesogloeal muscles in the tentacles and in the oral disc, in the arrangement of the reproductive organs 

 on filament-lacking mesenteries of the last order, in the number of tentacles in comparison to that of the 

 mesenteries etc., that there is no doubt that my species belongs to this genus. It is true, that the tentacles 

 of Sicyonis crassa, according to Hertwig, seem to be much more reduced than in my species, but tin's differ- 

 ence is, however, to my mind, only apparent, as the strong contraction and the bad preservation 1 in connec- 

 tion with a flattening of the tentacles in 5. crassa have produced the tubercle-shaped appearance of the 

 tentacles in the type. Thus it is to be supposed that the tentacles of S. crassa have had about the same ap- 

 pearance as those of S. tuberculata and ingolfi. Also the large apertures in the apex of the tentacles in the 

 type are certainly artificial products, due to bad preservation (compare further S. variabilis). Though Sicyonis 

 variabilis, described below, differs from the above named species in the arrangement of the mesenteries, it 

 seems to me that this species manifestly belongs to this genus. To the genus Sicyonis Cymbactis gossei, 

 described by Stephenson (1918 b p. 123), probably also may be referred. The whole organisation namely 

 indicates that we have to do with a Sicyonis, unfortunately Stephenson does not mention whether the fer- 

 tile mesenteries are devoid of filaments or not. Concerning the other species of Cymbactis, C. selaginella, des- 

 cribed by Stephenson (1918 a), may be a Stomphia 2 (compare this genus), and C. actinostoloides Wasil. and 

 C. maxima Wasil. belong to the genus Parasicyonis (compare p. 208). 



R. Hertwig 1888 has described a new species Sicyonis elongata. I cannot, however, arrange this 

 species in the series of Sicyonis, on account of the comparatively small breadth of the pedal disc and the pre- 

 sence of fertile mesenteries in the distal part of the body instead of in the proximal part, as in the real Sicyo- 



1 The Actinians from the Challenger-Expedition are generally very badly preserved and their original shape often greatly 

 altered by the pressure, of which I have been able to convince myself during a visit in London 1897. 

 1 After this was written Stephenson (1920 1. c. p. 559) has come to the same conclusion. 



27* 



