FEESH-WATEE POLYP 85 



Lay a wire across the top of the jar, and 

 from the wire suspend by means of a thread 

 a second scrap of meat out in the water a dis- 

 tance of an inch or two from the side of the 

 jar and near another group of hydras. Do any 

 of the hydras get out to the meat ? If so, how ? 

 Judging from these experiments, what methods 

 of locomotion would you ascribe to the hydra ? 



h. Nutrition. — Put a few scraps of raw beef about as 

 large as the head of a pin into a watch-glass con- 

 taining two or three hj'^dras, and watch with the 

 low power or with a hand-lens to see the behav- 

 ior of the animals. In what way do they seize 

 the meat? How is it conveyed to the mouth? 

 How swallowed? With the hand-lens carefully 

 examine a number of specimens attached to the 

 inside of the glass jar to see whether or not you 

 can find any which have caught any of the water 

 fleas or other small crustaceans which were put 

 in with the hydras. How does the hydra behave 

 when any of the crustaceans come in contact 

 with it? "What apparently happens to the crus- 

 tacean ? Look for hydras which have swallowed 

 small water animals, and note their position and 

 condition in the body of the hydra. 



c. Nervous Properties. 



1. Irritability. — Is the hydra disturbed when irri- 

 tated by coming in contact with a foreign 

 body, as when gently touched once with a fine 

 bristle ? "What does the animal do under such 

 circumstances ? What is its behavior upon be- 

 ing touched repeatedly ? 



