DEVELOPMENT OF JELLY- FISHES. 



67 



shorter and thicker than in the males. The eggs pass out 

 of the mouth into the water along the channeled arms, and 

 in October the ciliated gastrula becomes pear-shaped and 

 attaches itself to rocks, dead shells, or sea- weeds, and then 

 assumes a Hydra form with often twenty-four very long 

 tentacles. This stage was originally described as a distinct 

 animal under the name of Scypliistoma. In this Scyphis- 

 toma stage (Fig. 45) it remains about eighteen months. 

 Toward the end of this 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 



Fig. 48. 4.urelia flavidula. After Agassi/. 



out, and the animal assumes the Strobila stage (Fig. 46). 

 Finally, the disks separate, the upper one becomes detached 

 and with the other disks swims away in the Epliyra form 

 (Fig. 47), when about a fifth of an inch in diameter, and 

 toward the middle or end of summer becomes an adult 

 Aurelia (Fig. 48). 



Though the Aurelia has lasso-cells it is not poisonous to 

 bathers. Not so, however, witli the gigantic Cyanea arctica, 

 whose long tentacles are poisonous ; fishermen as well as 

 bathers being often annoyed by them. This giant jelly-fish 

 sometimes attains a diameter of from three to five feet across 



