MOW JELLY-FISH GROW. 
25 
ous branches, which connect with the marginal vesseL 
The Aurelia spawns late in the summer. 
The eggs pass out of the mouth into the water along the 
channelled arms, and in October the ciliated sac or gastrula 
becomes pear-shaped and attaches itself to rocks, dead 
shells, or sea-Aveeds, and then assumes a Hydra form with 
often twenty-four very long tentacles. This stag^ ij^as 
Fig. ^^.—Sertularia ahietina of Europe. A, natural size; B, magnified, show 
in^ the cells containing the animals. 
originally described as a distinct animal under the name oi 
ScypMstoma, In this Scyphistoma stage (Pig 24) it re- 
mains about eighteen months. Toward the end of thia 
period the body increases in size and divides into a series of 
cup-shaped disks. These saucer-like disks are scalloped on 
the upturned edge, tentacles bud out, and the animal as- 
sumes the Strobila stage (Fig. 25). Finally, the disks sep- 
arate, the upper one becomes detached and dies, but the 
