CERIANTHARIA. 



Whether a cnido-glandular tract region is to be found I cannot determine with certainty. Probably 

 there is none, but on the other hand the ciliated tract region is continued in to a craspedion region. 

 Metamesenteries i bear "acontia". On the other mesenteries no such formations are found, though 

 it is likely enough that in older specimens they are borne by a further couple of mesenteries. 



The regions of the ciliated tracts in the metamesenteries of the 3rd and 4th cycles are parti- 

 cularly short, whilst the cnido-glandular tract is remarkably coiled, and very long. Almost the whole 

 of the free border of the mesentery is taken up by the cnido-glandular tract 



As to the structure and arrangement of the mesenterial filaments and their differentiations 

 there seems to be a correspondance with Arachnanttms oligopodus. Though I cannot indicate the 

 boundary between the regions of the ciliated tracts and the craspedia regions on protomesenteries 2 

 and on the metamesenteries of the ist and 2nd cycles, the craspedia regions seem to have about the 

 same extent on these as in Arachnanthus oligopodus. The median streak is constructed as in that 

 species, as also the craspedia and the "acontia". As the description of the structure of the region of 

 the ciliated tracts, of the craspedia regions and the "acontia" finds its place in the morphological des- 

 cription of Ceriantharia (Section 4) I have not thought it needful to go into their structure in detail 

 here. The thick-walled nematocysts in the cnido-glandular tract have a length of about 26 36^. 

 In the endoderm of the mesenteries occur, especially in the lower part, large curved nematocysts of 

 as much as 72 // in length. 



The mesenterial muscles shew the typical arrangement and are strongly developed, particularly 

 if we take into consideration the small size of the animal. They are quite distinct along the whole 

 length of the stomatodaeum, and are the best developed muscles I have observed in any Ceriantharia. 



The metamesenteries of the ist and 2nd cycles are fertile with feebly developed reproductive 

 organs, the rest sterile. The species is hermaphrodite. 



Systematic remarks. Though the tentacles are torn away on the only specimen discovered, 

 so that it is impossible to attempt to study their arrangement, yet from the other morphological facts 

 the inference might be drawn that this species is the adult animal of the larval Ceriantharium 

 described by Sars, Arachnactis albida, or at least is very closely related to this larval form. The 

 descriptions of this larval form given by Vanhoffen (1895) and v. Beneden (1898) as well as my 

 own investigations of the same form, an account of which is given below, agree very largely with 

 A. sarsi. In fig. 4 Plate i in Vanhoffen's work is represented an Arachnactis albida which is very 

 like the specimen described above. In particular the appearance of the stomatodaeum is strongly 

 suggestive of the stomatodaeum in the species I have here described, as also the appearance of the 

 "acontia". The anatomical study which I have made of the "acontia" in A. albida also tends to shew 

 that we have the same species before us. The colour markings too of the two forms agree very well 

 together. It is'noticeable moreover that the specimen of A. sarsi in respect to the number of the 

 mesenteries ranks but little above the largest known specimens of A. albida. There is only a difference 

 of a few couples of mesenteries. 



However as it cannot be positively settled whether the species here described is the adult 

 animal of A. albida, and as it does not seem advisable to identify them without convincing proof, I 

 have preferred to give this species a new name A. sarsi. I do this the more readily as there seems 



