ACALEPHS. 



507 



tral portion and unite with a circular tube which follows 

 the outline of the periphery of the animal. The external 

 edges of the central or oral Fig. 492 . 



opening are turned outward, 

 and more or less prolonged in- 

 to fringe-like appendages. Ten- 

 tacular appendages wanting, or 

 present in almost every de- 

 gree of development both as 

 regards number and extent. 

 Jelly-Fishes,in their most com- 

 mon forms, are known as Me- 

 dusae, and have long been ob- 

 jects of great interest to voy- 

 agers and residents by the sea, 

 as well as to the most learned 

 naturalists. Their jelly-like 

 bodies, scarcely denser than 

 the water in which they move ; 

 their curious and beautiful 

 forms, and often beautiful colors ; their complicated struc- 

 ture, delighting all who study it; their movements, varied 

 and graceful as those of the butterfly or the bird of the 

 air ; their phosphorescence by night, making the track of 

 the vessel, and the breakers upon the shore, glow with 

 light, and gaining for them the appellation of " Lamps 

 of the Sea" ; and, above all, their wonderful modes of re- 

 production and development, conspire to excite our in- 

 terest, our wonder, and, as we study them carefully, our 

 admiration. 



In treating this group, we follow Agassiz, in his " Con- 

 tributions to the Natural History of the United States." 



Jelly-Fishes embrace three orders, Ctenophorae, Dis- 

 cophorae, and Hydroids, ranking in the order named, 

 Ctenophorae being highest. 



Jelly-Fish, P. cyanella, Per. & LeS 



