FIELD BOOK OF PONDS AND STREAMS 



Hydra viridissima (viridis) (Fig. 90). — Green hydra. Body 

 grass-green; about 6 short tentacles; male and female organs 

 on the same individual, usually in summer. 



Fig. 91 — Gray hydra, Hydra vulgaris. 



Hydra vulgaris (grisea) (Fig. 91). — Body gray, orange, or 

 brownish; about 6 tentacles; male and female organs usually 

 on different individuals, in summer; 4 kinds of stinging cells. 



Fig. 92. — Brown hydra, Hydra oligactis. 



Hydra oligactis (fusca) (Fig. 92). — Brown hydra. Body 

 brownish, very slender at the proximal (attached) end; about 

 8 very long tentacles; 3 kinds of stinging cells. Difficult to 

 separate from H. vulgaris except by microscopical examina- 

 tion of the stinging cells. 



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