46 R- T. Günther 



ave jibout twice as broad as liigb. I bave not actually seen cilia 

 lipon tbem, but currents, rendered visible by particles suspended 

 in tbc fluid, made it quite clear tbat tbe cells must be furnished 

 witb vibratile processes. 



Tbe epitbelium of the circulav canal is of a like nature. In 

 transverse sections it would appear tbat tbe radial canals are en- 

 compassed by about 8 cells, wbereas 6 are sufficient to go round 

 tbe circular canal of smaller girth (figs. 11, 22). 



Endoderm of Tentacles. 



In tbc bollows of tbe tentacles the endodermal lining becomes 

 tbicker and tbe cells more columnar. Each cell has a flagellum. 

 Tbe nuclei are situated dose to the attachment of tbe flagellum 

 near the outer end of tbe cell (fig. 23). Many of the cells are 

 vacuolated, a single large vacuole next tbe mesogloea in each, and 

 some contain large spherical droplets which are stained brown in 

 osmic preparations but are yellow in tbe live organism. 



It will be noticed tbat tbe nuclei and vacuoles bave the same 

 relative disposition both in the endoderm and in tbe ectoderm. The 

 nuclei are situated nearer to, and tbe vacuoles are situated further 

 from, tbe axis of the tentacles. 



In tbe reduced tentacles i. e. in those which do not bear cnido- 

 phors but are reduced to mere stiimps, the endoderm cells are of a 

 taller form. On comparing tbe section through such a stumpy, re- 

 duced tentacle (fig. 24) witb tbe section through a fully developed 

 tentacle, part of which is shown in fig. 16, we are led to tbe con- 

 clusion tbat the total uumber of endoderm cells is very much tbe 

 same in each of tbe two cases, altbough in tbe one case tbe endoderm 

 cells are very closely packed togetber and contain few or no inclu- 

 sions (vacuoles etc.), wbereas in tbe other case the cells are much 

 expanded and contain many inclusious. Tbe endoderm cells in the 

 cnidophor, hearing tentacles are cusbion-like and distended; those 

 of the reduced tentacles are compressed. A possible explanation of 

 this difforcncc seems to me to be tbat tbe cnidophorous tentacles 

 are in need of some extra skeletal support for tbe proper performance 

 of their functions. This support is atforded by the turgidity of 

 the distended endoderm cells as is also tbc case in many other 

 Hvdrozoa. 



