304 ELEMENTS OF COMPARATIVE ZOOLOGY. 



SUBCLASS II. SCYPHOMEDUS^: (Jellyfishes). 

 At first sight these Scyphomedusae differ greatly from 

 the Actinozoa. They are free-swimming forms in which 

 the body is developed into an umbrella-shaped structure, 



FIG. 138. Common white jellyfish (Aurelid). After Agassiz. 



the mouth is at the end of a long proboscis, and all is 

 semitransparent. Yet when the details of structure are ana- 

 lyzed there are found the same inturned oesophagus, the 

 same septa and filaments, and the same tentacles; and 

 hence these forms must be somewhat closely associated with 

 the sea-anemones. The jelly-like consistency of their bodies 

 has given them the name of Jellyfishes. A rather more 

 accurate name for them is medusae, the tentacles being 

 compared to the snaky locks of that mythical monster. 

 They swim through the water by a lazy flapping of their 

 umbrellas, feeding upon whatever may come in their way. 

 While some are small, others become veritable giants, the 

 large blue jellyfish of the New England coast sometimes 

 measuring seven feet across ; its tentacles streaming behind 

 for a hundred feet as it swims through the water. 



