IV 



PHYLUM CCELENTERATA 



165 



a meduzoid (y), and a large enveloping bract (t). The stem often 

 breaks at the internodes, and the detached groups of zooids then 

 swim about like independent organisms. 



Porpita is formed on a different type, and has a close general 

 resemblance to a medusa. It consists (Fig. 124) of a discoid 



FIG. 123. Diphyes campanulata A, the entire colony; B, single group of zooids. , 

 cosnosarc ; c, cavity of swiniming-bell ; c, groups of zooids ; (/, medusoid ; i, grappling line or 

 tentacle ; m, swimming-bell ; n, polype ; o, mouth of swimming-bell ; t, bract. (From 

 Parker's Biology, after Gegenbaur.) 



body, enclosing a chambered chitinoid shell (s/i) containing air, and 

 obviously corresponding with the float of Physalia. The edge of 

 the disc is beset with long dactylozooids (tf) and from its lower 

 surface depend numerous closely set blastostyles provided with 

 mouths and bearing medusae, while in the centre is a single large 



