48 



HYDROZOA. 



for the ova during the earlier 



stages of thei 



development {fig 



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 Lucernaeidje : — a, Rhizostoma pulnw; ft 

 Chrysaora hysoscella ; c, its lithocyst. (All reduced.) 



fr 



is 



lined by a layer of endoderm which sends pr°" 

 longations into the system of anastomosing canals, 

 communicating with a marginal vessel, fringed, m 

 its turn, by a series of tentacular diverticula. The 

 generative products are lodged in saccular p r0 * 













