28 



CERIANTHARIA. 



contains, besides supporting cells, principally nematocysts with coiled spiral thread (the length of the 

 neraatocysts varies greatly and may reach to 103 /z) and mucus cells. The nematocysts are more 

 numerous in the upper part and the mucus cells in the lower part of the column where they are 

 closely packed together. The ectodermal musculature of the column is extremely developed; for the 



size of the animal it is the most strongly developed longitu- 

 dinal musculature that I have observed in any of the Ceri- 

 antharia. 



The stomatodaeum has the same structure as in Arach- 

 nanthus oligopodus. The ridges in the aboral part therefore 

 are not supported by mesogloeal processes. The ectoderm is 

 very thick and contains nematocysts of varies forms, now 

 resembling those found in the column, now spirocysts, now 

 thick-walled and granulated, larger (55 60 p and smaller 31 

 41;*). The siphonoglyph is of the usual structure with speci- 

 ally numerous mucus cells on the boundary of the stomatodaeum. 

 The ectodermal musculature of the stomatodaeum and sipho- 

 noglyph is feeble but distinct 



The mesenteries (Textfig. 5): 



The directive mesenteries are comparatively long. 

 Protomesenteries 2 agree in appearance with the meta- 

 mesenteries of the ist and 2nd cycle (In consequence of the 

 animal's contraction all these mesenteries are somewhat folded. 

 See diagram). The ciliated region is long, but so far as I have 

 been able to see from the anatomical examination, the region of 

 the cnido-glandular tract is absent, as in A. oligopodus. On 

 the other hand there is a craspedion region. They extend to 

 about the same length as the hyposulcus and are sterile. 



Protomesenteries 3 are sterile and rather longer than the 

 directive mesenteries; the ciliated tract region is very short, 

 the cnido-glandular tract region on the contrary very long 

 and very wavy. 



The metamesenteries of the ist and 2nd cycles are 

 little distinguished in length from each other, to judge from 

 the first two couples. The same is true of the metamesenteries of the 3rd and 4th cycles. The meta- 

 mesenteries of the ist and 2nd cycles are more than twice as long as those of the 3rd and 4th. The 

 longest of the former reach almost down to the aboral part of the body, whilst the latter run to half 

 or two-thirds of the length of the hyposulcus. I have not found any decided grouping of the meta- 

 mesenteries in quartettes. The metamesenteries decrease in length towards the multiplication chamber, 

 but this is not so clear with the mesenteries of the 3rd and 4th cycles. 



The metamesenteries of the ist and 2nd cycles are furnished with a long ciliated tract region. 



Textfigur 5. Diagram of the arrangement of 

 mesenteries and the stomatodaeum in Arach- 

 nanthus sarsi. For signs see explanation of 

 the figures. The boundaries between the cili- 

 ated tracts and the craspedia regions at m^ a 

 etc. are not marked as it was impossible to 

 observe them without microscopic 

 examination. 



