178 



ANIMAL BIOLOGY 



formed at the tip of each. It is now evident that we are looking at a 

 very tiny hydra. Finally the new individuals separate from the 

 column and begin an independent life. This method of reproduc- 

 tion is known as bidding. 



A, organ-pipe coral B, precious coral 



FIG. 126. Different forms of coral. 



C, sea-feather 



132. Suggestions for the study of hydra. Laboratory study. 

 Pupils should be supplied with living hydra if possible. The column 

 and tentacles should be observed by the aid of a magnifier, described 



and drawn. The animal 

 should be touched and the 

 action of the column and 

 tentacles noted and de- 

 scribed. If the hydra moves 

 from place to place, the 

 method of locomotion 

 should also be described. 



FIG. 127. Jellyfish. (Hargitt.) 



133. Relatives of hydra. 

 Among the relatives of 

 hydra are the corals (Fig. 126), sea-anemones, and jellyfish (Fig. 

 127). One form of ceral, the red coral, is of considerable economic 

 importance. In all the corals the column secretes a mineral sub- 



