CERIANTHARIA. 



33 



the terminations of protomesenteries 2 and 3. In other points tliey a<i^ree in strnctnre with proto- 

 mesenteries 2. They diminish in length towards the mnl- sl 



tipHcation chamber. The botrncnids are larger than in 

 protomesenteries 2. 



The metamesenterics of the 3rd and 4th cycles are 

 sterile and shorter than the preceding, thongh when fnll- 

 giown the oldest onght to reach a long wa>- down. ,The\- 

 decrease as usnal towards the mnltiplication chamber. 

 As too few nietamesenteries of the 3rd and 4th cycles are 

 developed, it is hard to say whether the difference in 

 length between them is considerable or not. As far as 

 can be jndged from the development of the mesenteries, 

 it seems not to be so. The metamesenterics of the 3rd 

 and 4th cvcles otherwise agree in strnctnre with proto- 

 mesenteries 3. 



P'rom the specimen represented (Textfig. 7) we see 



that the mesenteries of the left side are more developed 



than on the right, which is most nnnsnal with the Ceri- 



antharia. A fnrther pccnliarity is to be found in the fact 



that the highest part of protomesentery 2 on the left side 



is not found and its cnido-glandnlar tract has cohered 



with protomesentery 3 on the same side. (The upper 



part, which is mi.ssing, is marked throughout by lines and 



dots). Presumably the animal has been damaged in an 



embr\onic state, before the mesenteries took shape, and 



regeneration has brought about the irregularity as regards 



protomesenteries 2, as well as the better growth of the 



mesenteries on this side. Other specimens examined are 



normal. 



The filaments: The region of the ciliated tracts is 



well marked off and distinct. The mesogloeal processes 



that support the ciliated tracts issiie from the chief lamella 



of the mesentery as in C. lloydii and several others. The 



median streak is more semicircular in shape, in a few 



cases slightly flattened towards the sides. No trace of 



bipartition of the median streak can I)e detected. The the mesentery iprotomesentery 2) is lacking. !•• 



signs see explanation of the Plate.s. 

 ectodermal cells in the middle of the median streak are 



not lower than in other parts of the streak. The gland cells and nematocysts are evenly distributed. 



The spirocysts are very numerous and in addition thick-walled nematocysts (46//) occur though rareh'. 



The mesogloea in transverse section is something like a rounded s])ade or tongue with a narrower 



'llic Danish In^nlf-Expedilion V. 3. 



Textfigure 7. Itotrucitidifer norvcgiais. Diagram of 

 mesenteries and stoniatodaeuni. The line of dashes 

 and dots on the left side indicates that this part of 



"or 



