4 8 



THE HYDROMEDUSAE 



Fio. 55. Limnocnida from the oral surface (after Gtinther). 



manubrium and shallowness of the gastric cavity, it strangely resembles 



many Cuninae, and in bud- 

 ding from the manubrium, 

 it approaches the Antho- 

 medusae. No hydroid stage 

 has been observed in its life- 

 history. 



Limnocodium, on the 

 other hand, resembles more 

 closely Leptomedusae and 

 Trachomedusae (Figs. 52, 

 53). Its generative organs, of 

 which the male only have 

 been observed, are placed on 

 the radial canals, as in both 

 these orders ; but it has a 

 hydroid stage, a thing not 

 known in any Tracho- 

 medusan, known not to 

 occur in niany Trachome- 



Fio. 55fl. Diagram of the gemmation of the medu- 

 soid of Limnocodium. a, external ectoderm ; b, endo- 

 derm of the radial canals ; c, coelenteron of the hydroid ; 

 d, cavity of radial canal ; e, ectoderm of mannbrium ; J 11a _ 



/, rudiment of subumbral cavity ; g, cavity of maim- ( lsae and lb V Universal 



brium ; h, endoderm of manubriurn, with blind canals 

 (j) ; f, k, ectoderm of eutocodon. (After Fowler.) 



among Leptomedusae ; 

 the firm character of 

 bell and tentacles suggest Trachomedusan affinities. 



yet 

 the 



