DIPHYES AND PORPITA 



251 



minal mouth, like the manubrium of a medusa, surrounded 

 by a great number of structures like hollow tentacles {^y'). 



Fig. 59. — A, Porpita pacifica (nat. size), from beneath, showing disc- 

 like stem surrounded by tentacles {t), a single functional hydranth [hy), 

 and numerous mouthless hydranths {hy'). 



B, vertical section of P. mediterranea, showing the relative positions 

 of the functional {hy) and mouthless {hy) hydranths,  the tentacles, 

 and the chambered shell {sh). (a after Duperrey ; B from Huxley, after 

 KoUiker.) 



The discoid body is supported by a sort of shell having the 

 consistency of cartilage and divided into chambers which 

 contain air (b, sh). 



Accurate examination shows that the manubrium-like 



