80 HYDROZOA. 



4. Calycophoridce. — Hydrozoa, whose hydrosoma 



is free and oceanic, consisting of several 

 pol}^ites connected by a flexible, contractile, 

 unbranched coenosarc, the proximal extremity 

 of which is furnished with nectocalyces, and 

 dilated to form a somatocyst. Eeproductive 

 organs as medusiform gonophores, budded 

 from the peduncles of the polypites. 



5. Physo'phovidce. — Hydrozoa, whose hydrosoma 



is free and oceanic, consisting of several 

 polypites connected by a flexible, contractile, 

 seldom slightly branched, coenosarc, the 

 proximal extremity of which expands into a 

 pneumatophore, and is sometimes provided 

 with nectocalyces. Eeproductive organs, 

 more or less complex in structure, developed 

 upon gonoblastidia. 



6. Medusidce. — Hydrozoa, whose hydrosoma is 



free and oceanic, consisting of a single poly- 

 pite suspended from the roof of a nectocalyx, 

 furnished with a system of canals. Repro- 

 ductive organs as processes either of the 

 sides of the polypite, or of the nectocalycine 

 canals. 



7. Lucernaridce. — Hydrozoa, whose hydrosoma 



has its base developed into an umbrella in 

 the walls of which the reproductive organs 

 are produced. 

 The characteristics of these orders are indicated 

 more briefly in the subjoined analytical table. 



2. Order i : Hydridse The order Hydrida3 



contains but a single genus, Hydra, distinguished 

 from the few marine Hydrozoa which it approaches 

 in physiognomy by its peculiar habit and locomo- 



