JELLYFISHES AND HYDROIDS 





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A JELLYFISH is an umljrella-sliaped 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 a^jplies 

 well to the large jelly fishes 

 called Scyphowednsce, but 

 the smaller kinds called 

 IhjdrmiicdusLC 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 

 with thousands of little 

 cells each containing a 

 minute coiled tube so slen- 

 der that it appears to be 

 a mere thread. When ex- 

 cited these cells burst, and 

 the little threads are shot 



Fig. S: PORTOGUESE MAN-OF-WAR. 



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

 ing with them a poison which cpiickly jjaralyzes a small fish. The 



