^ CERIANTHARIA. 



The stomatodaeum shews a similar structure to Arachnanthiis oUgopodiis and sarsi. The 

 longitudinal furrows of the stomatodaeum are here also unsupported by mesogloeal processes. They 

 are gradually transformed into the filaments as shewn in fig. 1—3, PI. 4. The siphonoglyph contains 

 extremely numerous mucus cells, especially in the upper part. The structure of the hyposulcus re- 

 sembles the siphonoglyph'.s, save that the mucus cells are less numerous. On the free border of the 

 hyposulcus a filamentous differentiation runs almost to the aboral end of it. The ectoderm of the border 

 contains numerous spirocysts and shews the same histological structure as the median streak. A 

 mesogloeal process supports a ciliated tract exactly as in Arachnactis lobiancoi and Aracluiantlius 

 oligopodus. 



The mesenteries. Van Beneden (1898) has given one or two good figures of their arrange- 

 ment. The oldest example represented by him was provided with 17 mesenteries. As to the sub- 

 division of the filaments my observations agree with van Bene den's. The "pelotons" of the filaments 

 are my cnido-glandular tracts, the upper straight-lined part is the region of the ciliated tracts, the 

 lower part also straight-lined below the cross stroke is the region of the craspedia (not marked on 

 metamesenteries 3 — mesenteries 5 — in van Bene den's fig. II), which van Beneden does not 

 distinctly mark, but merely as a single filament tract. 



The region of the ciliated tracts in transverse section resembles that of Arachiiaiithus oligopodus 

 and Araclinadis sarsi. The median streak has the same structure as Araclinanthus. A little way 

 below the stomatodaeum it is divided into 2 distinct portions separated from each other by a well 

 marked groove containing supporting cells. The groove is deep especially in large specimens or else 

 much flattened out like a broad plate— presumably the difference in appearance depends on a difference 

 of contraction in the filament. Besides, the ectoderm of the median streak is formed of the charac- 

 teristic cells. The mesogloeal processes, which support the portion of the ciliated tracts that lies towards 

 the column, issue from the mesogloeal portion of the median streak, not from the main lamella of 

 the mesentery. 



The cnido-glandular tract ("peloton") has the enlargement pointed out by van Beneden and 

 has the usual structure of thick-walled nematocysts and granular elongated gland cells, lying close 

 together. 



The craspedion i:)ortion shews the same division as the median streak in the region of the 

 ciliated tracts. It is either deep (fig. 7, pi. 5) or else flattened out rather. In the most aboral part it 

 is comparatively slight and shews no division. A well developed craspedion region is found on all the 

 more developed mesenteries of the ist and 2nd cycles. 



The so-called "acontia" have a structure exactly corresponding to that in Aracliiiantliiis oligo- 

 podus and sarsi (see further 4th section). Here too they are formed of a part of the ectodermal 

 filament, which contains mucus cells closely packed together. I have not observed any increased 

 agglomeration of nematocysts in the endodermal part of the "acontia". On the other hand large curved 

 nematocysts are found in the endoderm of the mesenteries (« fig. 7. PI. 5) esi3eciall\ in the aboral part 

 of the mesenteries. The appearance of the acontia to the naked eye is shewn by Vanhoffen (fig. 3, 

 PI. I, 1893). 



As regards the arrangement of the musculature, I have been able, b\- means of two examples 



