234 ALTERNATE GENERATIONS. 



surface of the water. The name gives no idea of 

 the animal as it exists in full life and activity. 

 When we speak of a Bird or an Insect, the mere 

 name calls up at once a characteristic image of 

 the thing ; but the name of Jelly-Fish, or Sun- 

 Fish, or Sea-Blubber, as the larger Acalephs are 

 also called, suggests to most persons a vague idea 

 of a fish with a gelatinous body, or, if they 

 have lived near the sea-shore, they associate it 

 only with the unsightly masses of jelly-like sub- 

 stance sometimes strewn in thousands along the 

 beach after a storm. To very few does the term 

 recall either the large Discophore, with its pur- 

 ple disk and its long streamers floating perhaps 

 twenty or thirty feet behind it as it swims, or 

 the Ctenophore, with its more delicate, trans- 

 parent structure, and almost invisible fringes in 

 parallel rows upon the body, which decompose 

 the rays of light as the creature moves through 

 the water, so that hues of ruby-red and emerald- 

 green, blue, purple, yellow, all the colors of the 

 rainbow, ripple constantly over its surface when 

 it is in motion, or the Hydroid, with its little 

 shrub-like communities living in tide-pools, estab- 

 lishing themselves on rocks, shells, or sea-weeds, 

 and giving birth not only to animals attached 

 to submarine bodies, like themselves, but also to 

 free Medusae or Jelly-Fishes that in their turn 

 give birth again to eggs which return to the 



