36 CCELENTERATA AND 



Halecium. Plant-like, branched, rooted by creeping 

 stolon. Hydrothecse biserial, tubular, bell-shaped, sub- 

 sessile, jointed to short lateral process. Hydranth par- 

 tially retractile. Fixed sporosacs. 



H. gracile. 



Lovenella. Stem simple, branched, thread-like stolon. 

 Hydrotheca turbinate, elongate, crowned with a conical 

 operculum. 



L. gracilis. 



Clytia. Stem simple, branched slightly. Creeping 

 stolon. Hydrothecse bell-shaped. No operculum. Hy- 

 dranths with large trumpet-shaped proboscis. Medusae on 

 stolon and stem. 

 Medusa, Clytia. 



C. Johnstoni. 



Obelia. Stem branching, plant-like, creeping stolon. 

 Bell-shaped. No operculum. Gonothecse on stem and 

 branches. 



0. gelatinosa. 

 commiwrdlis. 



Campanularia. Stem simple, branched, filiform stolon. 

 Hydrothecae bell-shaped. No operculum. Hyaline. Hy- 

 dranths with cup-shaped proboscis. 



Gonophores fixed sporosacs, which mature in the cap- 

 sule. 



(7. caliculata. 



Thaumantias. Stem simple or branched, rooted to 

 thread-like stolon. Calycles campanulate, with funnel- 

 shaped proboscis. 



Gonothyrcea. Stem erect branching, thread-like stolon. 

 Hydrothecse bell-shaped, transparent. Proboscis promi- 

 nent, contractile. 



G. tennis. 

 Campanulina, Stem slender, annulated. Calycles thin, 



