48 



HYDROZOA. 



for the ova during the earlier stages of their 

 development {fig. 7, h). The interior of the poly- 

 pite leads to a large central cavity, situate in the 

 substance of the thick gelatinous umbrella, and 



Fig. 7. 



Oceanic forms of Luceexaeid^ : — a, Ehizostoma ^ulmo ; b, 

 Chrysaora hysosceUa ; c, its litliocjst. (All reduced.) 



lined by a layer of endoderm which sends pro- 

 longations into the s^^stem of anastomosing canals, 

 communicating with a marginal vessel, fringed, in 

 its turn, by a series of tentacular diverticula. The 

 generative products are lodged in saccular pro- 



