THE CCELENTERATA 



55 



and better maintains its integrity under the ordeal 

 (see Fig. 21). 



Rhizostoma grows to a large size. I had one brought 

 to me a little while ago which proved a good wheel-barrow 



Fig. 21 



Rhizostoma. % Natural size 



Chrysaora. | Natural size 



load for a strong man, but the usual size is from six to ten 

 inches across. 



The general form of the larger medusa can be roughly 

 described as a circular disc, umbrella-shaped, the disc 

 partially or entirely closed beneath by a membrane. 



Sensory organs, tentaculocysts, hang from the margin 

 (they are not present in Rhizostoma), while from the centre 

 long in some species, shorter in others hangs an appendage 



