CCELENTEEATA AND PORIFERA 173 



fore said to exhibit alternation of generations) i.e., the egg 

 of the medusa generation does not hatch into a medusa, 



FIG. 202. Half of a jellyfish ; a, two of the four arms around the mouth m ; r, 

 reproductive organs ; st, stomach ; t, tentacles 



but develops into a fixed colony some of whose polyps 

 produce medusa? (small jellyfish). 



The large jelly fishes of the ocean, which are similar hi 

 structure to the medusse just described, attain a diameter 

 of several inches and possess tentacles a foot or more long 



