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. 



