CCELENTEEATA. 19 



E. Drawings, etc. 



1. Make a clay model of a Hydra. 



2. Cut out of paper a model of (1) a cross-section, (2) 



a longitudinal section. Color ectoderm white 

 or blue, endoderm yellow and tlie partition-mem- 

 brane red. 



3. Make a careful drawing of a typical Hydra (5 cm.). 



4. Make a diagram of a cross-section (3 cm.). 



Note : Sections F, G and H require observations for several 

 successive days. 



F. Locomotion. 



1. What evidence can you give that the Hydra changes 



its position in the aquarium ? (Devise some plan 

 for proving this.) 



2. Is the Hydra's hold on the jar or leaf easily loosened? 



(Try to detach a Hydra with a camel's-hair brush.) 



3. Does the Hydra drop to the bottom when loosened ? 

 By what means does the Hydra move from place to 



place ? 



G. Feeding-. 



1. How does the Hydra seize and swallow food ? (Try 



to feed the Hydra with bits of meat or with small 

 crustaceans.) 



2. How is the Hydra able to catch swimming animals ? 

 What is the natural food of the Hydra ? 



Where must the Hydra live to find this food most 

 plentiful ? 



H. Keprocliiction. 



1. Budding. 



A small Hydra called the bud sometimes grows from 

 the side of another Hydra. 



