ALTERNATE GENERATIONS. 261 
a depression, forming a stony cup filled with. 
purest sea-water, and overhung by a roof of rock, 
which may be fringed by a heavy curtain of 
brown sea-weed, the rosy-headed, branching Eu- 
dendrium, one of the prettiest of the Tubula- 
rians, may be found. Others choose the tide- 
pools, higher up on the rocks, that are freshened 
by the waves only when the tide is full: such are 
the small, creeping Campanularians. Others, 
again, like the tiny Dynamena, prefer the rougher 
action of the sea; and they settle upon the 
sides of rents and fissures in the cliffs along the 
shore, where even in calm weather the waves 
rush in and out with a certain degree of violence, 
broken into eddies by the abrupt character of 
the rocks. Others seek the broad fronds of the 
larger sea-weeds, and are lashed up and down 
upon their spreading branches, as they rock to 
and fro with the motion of the sea. Many live 
in sheltered harbors, attaching themselves to 
floating logs, or to the keels of vessels ; and some 
are even so indifferent to the freshness of the 
water that they may be found in numbers along 
the city-wharves.* 
Beside the Jelly-Fishes arising from Hydroids, 
* Those who care to_know more of the habits and structure of 
these animals will find detailed descriptions of all the various species 
of our coast, illustrated by numerous plates, in the fourth volume of 
my Contributions to the Natural History of the United States, pub- 
lished some time ago. 
