PHYLUM CCELENTBRATA 



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 



Fio. 123.— Diphyes campanulata A, the entire colony; B, single group of zooids, a, 

 coenosarc ; c, cavity of swimming-bell ; c, groups of zooids ; ff, medusoid ; i, grappling line or 

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

 Parker's Biology, after Gegcnbaur.) 



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 {t) and from its lower 

 surface depend numerous closely set blastostyles provided with 

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



