Descriptive Zoology. 



Development of the Scyphozoa. The egg, after being 

 fertilized, divides into many cells. These finally arrange 

 themselves into a two-layered sac. This becomes cylin- 

 drical and attaches itself by one end. The other end 

 opens to form a mouth, around which tentacles develop, 



FIG. 184. JELLYFISH. 



The four long projections are the oral (mouth) appendages. The slender hanging 

 projections are the marginal tentacles. 



thus forming a hydralike or polyp form. This elongates 

 and becomes constricted transversely so that it resembles 

 a pile of saucers, each of which is scalloped. These 

 saucer-shaped parts become detached in order from the 



