PROBLEM I. The Kinds of Animals of the Earth 



59 



Fig. 84 Sea ane7nones. These beautiful animals are several inches high. Where do they 

 live? How do they get their food? (naturf. magazine) 



green. The body is little more than a sac 

 in which food is digested. The mouth is 

 a slitlike opening in the upper end of the 

 sac; the tentacles that surround it grasp 

 the food which the water may wash 

 within reach. They can shoot out long 

 stinging hairs which paralyze or kill their 

 prey. Once the food is caught the ten- 

 tacles push it into the mouth. When the 

 tide goes out leaving the little anemone 

 in a rocky pool, it pulls in the tentacles 

 and contracts its body until it is nothing 

 but a small solid mound. 



Related to the sea anemones is hydra, 

 a tiny fresh water form. You may have 

 found it attached to the sides of an aquar- 

 ium. See Figure 85. 



Animals that make rock. Coral animals, 

 also, are attached to the sea bottoms. 

 They resemble sea anemones but differ in 

 several ways: they are usually much 

 smaller; they are attached to one another 

 in colonies; and they build shells of lime 



Fig. 85 Hydra, cut open and magnified. This is 

 a tiny anmial, seldom more than one fourth 

 inch long. Look for the mouth surrou?ided by 

 tentacles. These have stinging cells which can 

 kill small aniffials. 



Tentacles 



Body cavity 



Stinging cells 



Spermory 



Bud (will form 

 a new hydra) 



Ovary 



Part by which 

 Hydra attaches 

 itself 



