JELLYFISHES AND HYDROIDS 



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\ JELLYFISH is an umbrella-shaped creature with tentacles 

 -^^^ and sense organs arranged at intervals around the outer edge 

 of the umbrella, while the mouth and stomach occupy the position 



of the umbrella handle. 

 This description applies 

 Avell to the large jelly fishes 

 called Scyp]io))iednsce, but 

 the smaller kinds called 

 liydroniedusce have a deli- 

 cate membrane extending 

 inward all around from the 

 umbrella-edge forming a 

 diaphragm which partially 

 closes the opening of the 

 umbrella. Jellyfishes swim 

 by rythmatically opening 

 and closing their umbrella- 

 like bodies. 



Jellyfishes are carni- 

 vorous, feeding upon small 

 fishes, Crustacea, or one an- 

 other. They capture their 

 prey by means of their ten- 

 tacles which are armed 

 {^f I with thousands of little 



' < ^ '^ cells each containing a 



S ) minute coiled tube so slen- 



( '" der that it appears to be 



'') a mere thread. When ex- 



cited these cells burst, and 

 F,-^. 8; PORTUGUESE MAN-OF-WAR. ^j^g j-^^jg threads are shot 



out with such force that they penetrate the skin of the victim, carry- 

 ing with them a poison which quickly paralyzes a small fish. The 



