JELLY-FISHES. 



357 



thin membranous fins, set at regular distances, one 

 above tlie otber, wbicli may be considered as single 

 horizontal rows of cilia, agglutinated together into flat 

 plates. Each plate has a rapid movement up and down, 

 from the line of its insertion into the band, as from a 

 hinge, and thus striking the water downwards, like a 

 paddle. The whole band may be likened to the pad- 

 dle-wheeJ of a steamer, except that the paddles are set 

 in a fixed line of curvature instead of a revolving circle. 



The effect, however, is exactly the same : that of pad- 

 dling the beautiful little globe vigorously through the 

 water. The prismatic colours are produced by the play 

 of light on their glittering surfaces, which are ever pre- 

 sented to the eye of the beholder at changing angles. 



We rarely see these rows of paddle-fins wholly at 

 rest, but occasionally one or two bands will be alone in a 

 state of vibration ; or one or more will suspend their ac- 

 tion while the rest are paddling. Sometimes in a band 



