80 



HYDROZOA. 



4. Calycophoridee. — Ilydrozoa, whose hydrosoma 



is free and oceanic, consisting of several 

 polypites connected by a flexible, contractile 

 unbranched coenosarc, the proximal extremity 

 of which is furnished with nectocalyces, and 

 dilated to form a somatocyst. Reproductive 



as medusiform gonophores, budded 

 from the peduncles of the polypites, 



5. PhysophoridcE. — Hydrozoa, whose hydrosoma 



is free and oceanic, 







organs 



consisting 



„ of several 

 polypites connected by a flexible, contractile, 

 seldom slightly branched, ccenosarc, 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. Kepro- 



as processes either of the 



ductive organs 



canals. 



polypite 



7. Lucernaridw. — 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 1 : llydridae. — The order Hydride 

 contains but a single genus, Hydra, distinguished 

 from the few marine Hydrozoa which it approaches 

 in physiognomy by its peculiar habit and locomo- 



