AND RELATED GENERA, SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 61 



the Porponia stage, which Ilyanthopsis probably passes through during development, 

 is thus not apparent in the older individuals. The filaments seem to agree with those 

 in Halcurias and Porponia, but were so badly preserved that I could not obtain any 

 clear picture of them. In addition to spirocysts there are thick-walled nematocysts 

 like those in the body-wall (length 36 m), as also numerous thick-walled capsules with 

 distinct base to the spiral thread (length 31-34 m, greatest breadth 5 m). Sexual 

 organs are present on all the mesenteries. The animal is hermaphrodite. Well- 

 developed testes occurred distally inside the filament region in each mesentery, while 

 a few grape-like eggs were found in the proximal part. 



The investigation of Ilyanthopsis elegans has thus led to the result I imagined it 

 would, namely, that this is nearly related to Halcurias and Porponia. Though the 

 material is too small to permit of a detailed statement of the grouping of the tentacles 

 and mesenteries, there can be no doubt that they should be placed together. The 

 arrangement of the tentacles shows the same characteristics as in these genera, and 

 certain features of the mesenterial arrangement are the same apparently. Even the 

 external appearance agrees well with that of Halcurias : spirocysts occur in the body- 

 wall and oesophagus, as in the latter genus and Porponia. Ilyanthopsis shows most 

 resemblance to Halcurias, and it might be a question whether these two genera should 

 not be joined as one. For the time being, however, such a grouping would not be so 

 fortunate, as Ilyanthopsis has a much greater number of mesenteries than Halcurias . 

 further, in the former all the mesenteries are perfect, while in the latter about half are 

 perfect. Add to this that the longitudinal musculature of the mesenteries is strongly 

 developed in Halcurias, very weak in Ilyanthopsis, and it is evident that Ilyanthopsis 

 has its own developmental characteristics. It seems, moreover, more probable that 

 Ilyanthopsis has passed through a Porponia stage than a Halcurias stage, if the 

 mesenteries are taken into consideration. If we imagine all the mesenteries in Porponia 

 to be perfect, it is quite easy from them to derive the arrangement of the mesenteries 

 in Ilyanthopsis. In Halcurias, on the other hand, the stronger, not-directive mesen- 

 teries occur as unpaired mesenteries. How the development has proceeded we can 

 only learn from the younger stages. I consider it advisable, therefore, to set up a 

 new genus, Synhalcurias, for the species Ilyanthopsis elegans. The genus Ilyanthopsis 

 must be abolished, as the type species of this genus, Ilyanthopsis longifilis, E. Hertwig, 

 is no other than Condylactis passiflora, as stated by Pax (1910) ; I had also come to 

 this view in 1897 on examination of type specimens of the Challenger Actiniae in 

 London. 



We know of one more genus that might possibly be allied to Porponia, namely, 

 the genus Actinernus, founded by Verrill. From R. Hertwig's description of 

 Polysiphonia tuberosa ( = Actinernus tuberosus M'Murrich) and from M'Murrich's 

 description of A. plebeius, however, we can hardly conclude that a close relationship 

 exists between Porponia and these forms. According to my observations on a 

 specimen of Polysiphonia tuberosa from the Challenger Expedition, the arrangement 



