174 



SYSTEMATIC ZOOLOGY. 



the details of structure are analyzed 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, while 

 these same features together with the absence of a velum 



FIG. 21. Common white Jellyfish (Aureliu). After Agassiz. 



mark them off from the Hydrozoan jellyfishes (p. 166). 

 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 be- 

 hind for a hundred feet as it swims through the water. 



SUBCLASS III. CTENOPHORA. 



These forms, which are also called jellyfishes, differ 

 from the other ccelenterates in several respects. The body 

 is usually globular, instead of umbrella-shaped, and bears 

 on the surface eight rows, like meridians (fig. 22, c) of 

 vibratile organs, each row being composed of numerous 

 series of cilia, arranged much like the teeth of a comb 



