THE SEA-ANEMONE. 171 



into hyclra-like forms, which, on becoming attached, 

 give rise by a process of budding, to a hydroid colony, 

 some members of which assume a medusa form, thus 

 completing the cycle. This mode of development 

 has been called, though inappropriately, an alterna- 

 tion of generations. All jelly-fishes do not, however, 

 develop in this way. Jelly-fishes are richly supplied 

 with lasso-cells, and the larger ones sting severely, 

 being dangerous to bathers. 



Read the description of Cyanea and other jelly- 

 fishes in " Seaside Studies." 



THE SEA-ANEMONE. 



In its general form the sea-anemone resembles a hydra, 

 having a cylindrical hollow body attached by one end to 

 some foreign object, and at the free end a mouth sur- 

 rounded by tentacles. In its internal structure, however, 

 the sea-anemone presents some new features. The mouth, 

 instead of opening directly into the body cavity, as in the 

 hydra, opens into a stomach which hangs like a bag sus- 

 pended in this cavity ; the stomach has no bottom, but at 

 its lower end communicates freely with the body cavity. 



The body wall and stomach may be represented by a 

 glove-finger with its tip cut off and the open end turned 

 back part way into the larger part of the finger. 



The cavity of the body is divided into a series of radial 

 compartments by fleshy vertical partitions, the mesente- 

 ries, which extend inward from t lie body wall, some reach- 

 ing the stomach and being attached to it, others not ex- 



