CERIANTHARIA. 



In addition, thick-walled nematoeysts occur very rarely (length 24 26). The ectodermal musculature 

 is moderately developed (text-fig. 6), and is much feebler than in specimens of Cerianthus lloydii 

 of the same size. The connective tissue processes too on which the muscles rest are thinly scattered. 

 The structure of the tentacles shews no deviation from the Cerianthid type. The bulk of the 

 nematoeysts consists of spirocysts. In addition, thick-walled granulated nematoeysts are very frequently 

 found. They are rather larger in the marginal than in the labial tentacles (34 36^, 24 or 26^). The 

 ectoderm attains a considerable thickness; the ectodermal muscles are slight. 



The structure of the oral disc agrees with that of the tentacles ; the radial musculature is 

 rather more developed. 



The structure of the stomatodaeum agrees with that of the stomatodaeum of Cerianthus lloydii, 



save that the mucus cells are rarer. The nematoeysts are thick- 

 walled in the upper portion and agree with those of the labial 

 tentacles: in the aboral portion they are thick-walled, transparent, 

 and considerably larger (48 x 12 14//). The spirocysts are thinly 

 scattered. The ridges developed in the midmost portion of the 

 stomatodaeum are broader and only half as high as in C. lloydii. 

 As a result of this, the mesogloeal processes are broader and 

 shorter than in that species. 



The structure of the siphonoglyph also agrees in the main 

 with that of other Ceriantharia, though it is less differentiated 

 from the rest of the stomatodaeum. The mucus cells are sparser 

 than in C. lloydii. The structure of the hyposulcus and hemisulci 

 does not differ from that of the siphonoglyph. 



The mesenteries (text-fig. 7). The directive mesenteries are 

 small and insignificant, with no distinct hemisulcus. 



Protomesenteries 2 reach right down to the aboral pole, 



Textfigure 6. Botrucnidifer norvegicus. 

 Transverse section through a portion of 

 the column and stomatodaeum with the 



mesenteries at the upper part of the sto- and are the longest of the mes enteries. The region of the ciliated 

 matodaeum. dl directive chamber. 



tracts is about half as long again as the stomatodaeum. The 



region of the cnido-glandular tract shews no characteristic wavy coils but rests on a folded, very long 

 process issuing from the mesentery just where the region of the ciliated tracts ends. The region of 

 the ciliated tracts goes some way lip the process. The region of the craspedion is long, going right 

 down to the botrucnid in which the filament region ends. The botrucnids are smaller than on other 

 mesenteries (invariably?). Fertile. 



Protomesenteries 3 do not extend as far as the former, but still only terminate a little way 

 from the aboral pole. The region of the ciliated tracts is rather shorter and the botrucnid region 

 considerably longer than in protomesenteries 2. Sterile. Otherwise they resemble the mesenteries 

 just mentioned. 



The metamesenteries of the ist and and cycles, which are fertile, are long, and the latter 

 slightly shorter than the former in the same quartette. If those of the 2nd cycle are not fullgrown, 

 the difference is naturally greater. The termination of the ist metamesentery is intermediate between 



