CCELENTERATA. 



249 



profile and from below, 

 showing central polypite, 

 radiating and marginal 

 canals. 



fringed with tentacles, which are furnished with stinging 

 thread-cells. The radiating parts are in multiples of four. 

 Around the rim are minute colored 

 spots, the " eye - specks." In fine 

 weather, these " sea - blubbers " are 

 seen floating on the sea, mouth down- 

 ward, moving about by flapping their 

 sides, like the opening and shutting 

 of an umbrella, with great regular- 

 ity. They are frequently phospho- 

 rescent when disturbed. Some are 

 quite small, resembling little glass 

 bells ; the common Aurelia is over a 

 foot in diameter when full-grown; Flo . 196 ._ A M ed usa, se enin 

 while the Cyanea, the giant among 

 Jelly-fishes, sometimes measures eight 

 feet in diameter, with tentacles one 

 hundred feet long. The tissues are so watery that, when 

 dried, nothing is left but a film of membrane weighing 

 only a few grains. 



There are two representative types: the Lucernaria, 

 the Umbrella-acaleph, having a short pedicel on the back 



for attachment; tentacles 

 disposed in eight groups 

 around the margin, the 

 eight points alternating 

 with the four partitions 

 of the body -cavity and 



FIG. 197. Lucernaria auricula attached to a the four COl'IierS of the 

 piece of sea-weed; natural size. The one on ,1 i ,1 



the right is abnormal, having a ninth tuft of mouth J not l6SS thai! 



eight radiating canals, 



and no membranous veil. The common species on the 

 Atlantic shore, generally found attached to eel-grass, is an 

 inch in diameter, of a green color. Aurelia, the ordinary 

 Jelly-fish, is free and oceanic. It differs from the Lucer, 



