164 



ZOOLOGY 



SECT. 



It 



spending reduction of the rest of the coenosarc. The float (Fig. 

 123, pn) has the form of an elongated bladder, from 3 to 12 cm. 

 long, pointed at both ends, and produced along its upper edge 

 into a crest or sail (cr) : as a rule it is of a brilliant peacock-blue 

 colour, but orange-coloured specimens are sometimes met with. 



At one end is a minute 

 aperture communicating 

 with the exterior. There 

 are no swimming-bells, but 

 from the underside of the 

 float hang gastrozooids (p), 

 dactylozooids, branching 

 blastostyles (gonodendra) 

 with groups of medusoids 

 looking like bunches of 

 grapes of a deep blue 

 colour, and long retractile 

 tentacles (t), sometimes 

 several feet in length and 

 containing batteries of 

 stinging-capsules powerful 

 enough to sting the hand 

 as severely as a nettle. 

 The male reproductive 

 zooid remains attached, as 

 in Halistemma, but the 

 female apparently becomes 

 detached as a free medusa. 

 In Diphyes the float is 

 absent. Two swimming- 

 bells (Fig. 124, A, m) of 

 proportionally immense 

 size are situated at the 

 proximal end of the cceno- 

 sarc, and are followed by 

 widely-separated groups of 

 zooids (B), each group con- 

 no. 124. Diphyes campanulata. A, the entire taming a DolvPC (n) with 

 colony ; B, single group of zooids. a. coenosarc ; 

 c. cavity of swimming-bell ; e, groups of zooids ; 

 g, medusoid ; i, grappling-liue or tentacle ; m, 

 swimming-bell ; n, polype ; o, mouth of swim- 

 ming-bell ; t, bract. (From Parker's Biology, 

 after Gegenbaur.) 



Of 



its tentacles (i), a meduzoid 

 (g), and a large enveloping 

 bract (t). The stem often 

 breaks at the internodes, 

 zooids then swim about like 



and the detached groups 

 independent organisms. 



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

 resemblance to a medusa. It consists (Fig. 125) of a discoid 

 body, enclosing a chambered chitinoid shell (sh) containing air, and 



