FRESH-WATER HYDRA. 



32. Describe the nervous system. 



3.3. Describe the stomach. 



34. How chjes a starfish move? 



FRESH-WATER H\ ORA. 



Fresh-water hydras may be found in almost any 

 pond, and almost any time in tlie summer. They are 

 too small to be studied satisfactorily without a jnicro- 

 scope, but can readily be seen with a hand lens, or 

 with the unaided eye. 



1. Observe the size and the shape of the body. 



2. Notice how the body is fastened to the support 

 on which it rests. This end of the bod}^ is the foot. 



3. Observe the tentacles. How many? How 

 arranged? Are they smooth or warty? The mouth 

 is in the center between the tentacles. 



4. The rounded prominence upon, which the mouth 

 is situated is the hypostome. 



5. Perhaps a bud may be seen growing from the 

 side of the hydra. 



The hydra is the only 

 fresh-water representative 

 of a large branch of ani- 

 mals. 



The branch is called 

 Coelenterata, and includes 

 the Hydi-oids, Jelly fishes, 

 Corals, and many other 

 forms. It has no respira- 

 tory apparatus, no nei'vous 

 system, no heart or blood, 

 no stomach or digestive ap- 

 paratus. It has a perma- 

 nent body cavity, into which food is taken, and in 

 which it is digested, but the body wall itself acts as the 

 stomach. There is no separate stomach or intestine. 



FRESH-WATER BVDRA. 



