//. SC'TPIIOZOA. 



2i9 



minal, and often of lateral, budding. The lateral buds always 

 produce new seyphostomEe, the terminal, medusa3. In tlio latter 

 the scyphostonia develops into a strobila, becoming divided by 

 circular constrictions into a series of saucer-like discs, the youno- 

 jelly-fish. As the successive discs become ready they separate 

 from the pile and swim away as ' ephyrte. ' At first the ephyraa 

 (fig. 192) have only four gastral tentacles, parts of the gastral 

 folds of the scyphostoma (j). 21G); they lack marginal tentacles 



Fig. 196. — Development of AureUn auritn. (From Hatschek.) First row, j^rowtli of 

 planula to scyphostoma: Vjelow, strobilation (separation of epliyra^): left, oral view 

 of scypiiostoma ; ri^ht, two ephyrse. 



but have the eight lobes and the corresiionding sense pedicels. 

 Since the ephyras differ markedly from the adult medusaj and only 

 gradually change into the sexual form, the alternation of genera- 

 tions is complicated by a metamorphosis. This metamorphosis 

 persists in some cases {Pelagia noctiluca) where the alternation of 

 generations is suppressed; the egg develo2;)s directly into an 

 ephyra, which becomes transformed into the adult jelly-fish. On 

 the other liand no case is known where the medusa generation is 

 dropped out and the scyphostoma give rise sexually to other scy- 

 phostoma3. 



