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 hvdding. 



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 suppUed with living hydra if possible. The colunm 

 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 coral, the red coral, is of considerable economic 

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



