16 



HYDROZOA 



3. Colonies of other Calyptoblastea. (a) Sertularia, sessile polyps on both sides of branch. 

 ) Antennularia, sessile polyps on one side of branch ; nematocalyces. 



4. Pennaria. A colony of hydroids of the Gymnoblastea. 



5. Lizzia. (Type of the Anthomedusae). Manubrial gonad; groups. of marginal tentacles; ocelli. 



