132 



FIRST LESSONS IN ZOOLOGY 



some indeed being the immediate offspring of them, have 

 a body of quite different appearance. It corresponds in 

 general to an umbrella or bell (fig. 94), around the edge 

 of which are disposed numerous threads or tentacles 

 (corresponding to the tentacles of the polyp). The 



Fig. 94. — A jellyfish nr medusa, Goiiionema 'lertcns, eating two small fishes. 

 (Natural size; trom specimen fmm Atlantic Coast.) 



mouth-opening is at the end of a longer or shorter pro- 

 jection which hangs from the middle of the under side of 

 the umbrella, lil^e a short, thick handle. The body cavity, 

 or primitive stomach, extends out into the umbrella- 

 shaped part of the body. By alternately clapping shut 

 and opening the umbrella the jellyfish swims about. 



Jellyfishes occur in great numbers on the surface of the 

 ocean, and arc familiar t(i sailors under the name of 

 "sea-blubs." Some live in the deeper waters; a few 



