CERIANTHARIA. 



33 



the terminations of protomesenteries 2 and 3. In other points they agree in structure with proto- 

 mesenteries 2. They diminish in length towards the mul- 

 tiplication chamber. The botrncnids are larger than in 

 protomesenteries 2. 



The metamesenteries of the 3rd and 4th cycles are 

 sterile and shorter than the preceding, though when full- 

 grown the oldest ought to reach a long way clown. They 

 decrease as usual towards the multiplication chamber. 

 As too few metamesenteries 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 judged from the development of the mesenteries, 

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

 and 4th cycles otherwise agree in structure with proto- 

 mesenteries 3. 



From the specimen represented (Textfig. 7) we see 

 that the mesenteries of the left side are more developed 

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

 antharia. A further peculiarity is to be found in the fact 

 that the highest part of protomesentery 2 on the left side 

 is not found and its cnido-glandular tract has cohered 

 with protomesentery 3 on the same side. (The upper 

 part, which is missing, is marked throughout by lines and 

 dots). Presumably the animal has been damaged in an 

 embryonic 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 issue 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 be detected. The 

 cctodermal cells in the middle of the median streak arc 



Textfigure 7. Botrucnidiffr norvegicus. Diagram of 

 mesenteries and stoinatodaeuin. The Hue of dashes 

 and dots on the left side indicates that this part of 

 the mesentery (protomesentery 2) is lacking. For 

 signs see explanation of the Plates. 



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 (46/1) occur though rarely. 

 The mesogloea in transverse section is something like a rounded spade or tongue with a narrower 



D.tnisli In;;o!t"-K\pctlilion V. J. 



