18 HYDRACTINIID^E. 



the centre, and semitransparent toAvards the edge of the 

 body, and completely covered with cilia. Planulse which 

 had made their escape late in the evening, I have found 

 attached on the following morning. The cilia disappear, 

 and they fix themselves by one extremity, which expands 

 into a roundish disk, the body standing erect in the centre 

 of it. This gradually assumes the form of the polypite, the 

 upper portion becoming ovoid and pointed above. Three 

 or four tentacles also sprout from it, while the polypary 

 forms round the basal part. When the stem has reached 

 a certain height, it swells into small protuberances here 

 and there, which soon develope themselves into branches 

 and polypites. At the same time the base sends out 

 creeping shoots, from which fresh stems originate ; and the 

 process of germination continues until a whole forest of 

 plant-like structures has been evolved from the single 

 primary zooid. 



Hob. On an old submerged boat, Grand Canal, Dublin 

 (G. J. A.) : in the Commercial and other Docks, London, 

 on wood, &c. (Dr. Bowerbank) : in a cistern at Kensing- 

 ton (Busk) : near Lynn Regis (Dr. Low) . 



[G&lo-strat, Baltic (Lindstrom) : near Stockholm (Ret- 

 zius) : Schleswig (Van Beneden) .] 



Family II. Hydractiniidae. 



POLYPJTES claviform, sessile, with a single verticil of fili- 

 form tentacles round the base of a conical proboscis, 

 borne on an expanded and continuous crust ; the cceno- 

 sarc naked above. 



