//. SCYPHOZOA. 



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

 produce new scyphostomae, the terminal, medusae. In the latter 

 the scyphostoma develops into a strobila, becoming divided by 

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

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

 from the pile and swim away as ' ephyrae/ At first the ephyrae 

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

 folds of the scyphostoma (p. 246); they lack marginal tentacleSj 



FIG. 196. Development of Aurelia aurita, (From Hatschek.) First row, growth of 

 planula to scyphostoma; below, strobilation (separation of ephyree): left, oral view 

 of scyphostoma ; right, two ephyree. 



but have the eight lobes and the corresponding sense pedicels. 

 Since the ephyrae differ markedly from the adult medusae 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 noctilu-ca) where the alternation of 

 generations is suppressed; the egg develops directly into an 

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

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

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

 phostomae. 



