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mucus cells as well as very numerous granular gland cells and spiro- 

 cysts; it is therefore not so differentiated as the siphonoglyph. The 

 hemisulci are distinct, ver)' long and narrow in the lower part, fila- 

 ment-like as in P. vuiltiplicatus^ and provided with numerous spiro- 

 cysts and mucus-cells, but with thick-walled nematocysts also. 



The mesenteries: The arrangement of the mesenteries and 

 filaments is shewn in fig. 5, PI. 4 and the schematic text-fig. 4, 

 which is based on a series of sections of a young specimen. Van 

 Beneden's diagram (1898, Fig. A p. 25) on the other hand is based 

 on a rather older specimen. As van Beneden seems not to have 

 taken notice of the cnido-glandular tract of the mesenteries of the 

 1st and 2nd cycle, these are^ not marked on his figure. 



The directive mesenteries are short. The free part does not 

 attain the length of the stomatodaeum, and is considerably shorter in 

 younger specimens. The hemisulci possess no differentiated ciliated tract. 



The protomesenteries 2 are fertile and reach to the aboral 

 pole. The ciliated tract region extends further down than on other 

 mesenteries, but is nevertheless comparatively short and attains at 

 most a length of 172 times the stomatodaeum. The cnido-glandular 

 tract region is short, on a thread-like outgrowth of the mesentery more 

 or less resembling an acontium. The craspedion region is very long. 



The protomesenteries 3 are sterile, short, and scarcely reach 

 to the beginning of the cnido-glandular tract region of protomesen- 

 teries 2. The ciliated tract region is short and smaller than in the 

 mesenteries just mentioned. The region of the cnido-glandular tract 

 is better developed in these than in any of the other mesenteries and 

 has many coils. 



The metamesenteries of the ist and 2nd c\cles are almost 

 equally well developed, the older reach right down to the aboral pole, 

 the younger go a longer or shorter distance down the column. The 

 ciliated tract region is comparatively short, the region of the cnido- 

 glandular tract slight as on protomesenteries 2, with which the 

 mesenteries of the ist and 2nd cycle agree generally in structure. 

 The younger the mesenteries are, the shorter is the ciliated tract 

 region and the more oral the situation of the cnido-glandular tracts; the 

 cnido-glandular tract is found furthest towards the aboral side of the 

 animal in protomesenteries 2. These metamesenteries are all fertile 

 with the exception of the very youngest. 



The metamesenteries of the 3rd and 4th cycles are sterile and 

 agree in appearance and structure with protomesenteries 3. The 



