934 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- 
¥ish, 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 isin 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 Meduse or Jelly-Fishes that in their turn 
give birth again to eggs which return to the 
