XXII 



DIPHYES AND PORPITA 



251 



minal mouth, like the manubrium of a medusa, surrounded 

 by a great number of structures like hollow tentacles (hy 1 ). 



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 

 Kolliker.) 



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

 consistency of cartilage and divided into chambers which 

 contain air (B, s/i). 

 Accurate examination shows that the manubrium-like 



