HYDE0Z0A. 



29 



%x 





■ 



zoon the entire somatic cavity may be said to 

 perform the functions of a nutritive apparatus 

 {fig. 5, b). But the true digestive process is 

 chiefly effected within the bodies of the poly- 

 ; ^j pites. 



Each polypite exhibits two regions, a distal, and 



ft a proximal. The distal extremity terminates in a 



M delicate, more or less extensile, lip, which, in 



Fap : the Calycophoridce and Physophoridw, becomes 



everted and trumpet-shaped. Not unfrequently, 

 i th e the lip is lobed, its lobes, usually four in number, 



in some cases, very much prolonged [fig. 



be* 



abr 



he L 



)k 



i, perk 



v 



H 



bein_ 



Hyd 



CorynidcB, the proximal end 



polypite 



closed by the hydrorhiza, but throughout the re- 

 mainder of the class, it freely opens into the 

 somatic cavity. 



Many Calycophoridce and Physophoridce have 

 ■ h the proximal or attached division of the polypite 



produced into a more or less elongated peduncle, 

 beyond which may be recognised two distinct re- 

 gions ; a median, or gastric, and a distal, or oral. 

 The gastric cavity is separated from the interior of 



il • ^ mm -._ 



wt 



or < pyloric valve,' which is best seen among the 



Calycophoridce. 



Huxley 



describes it as " a strong circular fold of endoderm, 

 whose lips, when the valve is shut, project into 



f ] the cavity of the gastric, or median, division of 



the polypite. As the oily or albuminous globules 

 which result from the digestive process are formed, 



; " they usually accumulate close to the valve, and 



are kept constantly rotating by the cilia which 

 line the gastric chamber. After remaining for 



