S6 A GUIDE FOR THE STUDY OF ANIMALS 



2. How many tentacles has the hydra that you are study- 

 ing ? What does the hydra do with these tentacles when 

 it is expanded ? What is the probable object of such 

 actions ? 



3. How does a hydra respond to contact ? What seems 

 to be the object of such a response? 



4. Notice the location of the hydras in the large, undis- 

 turbed aquaria. Where are they placed as regards the 

 light side of the aquarium ? Of what value is such a re- 

 sponse to light in their case ? 



5. How can a hydra locate the small animals which are 

 its food ? 



How can it capture them ? 



6. What motions may a hydra perform, while remaining 

 attached by its base ? What are the results of these move- 

 ments ? 



7. If you have happened to see a hydra move from one 

 place to another, describe the process. If not, give the facts 

 which lead you to believe that it is able to do so. Suggest 

 all the methods you think it may be able to use. What is 

 your opinion of the hydra's power of locomotion } Of what 

 use is it in getting food ; in escaping enemies ; in following 

 the fluctuations of the water supply ? If you had to class 

 the hydra as either one, would you call it a stationary or a 

 locomotory animal ? 



8. Study budding hydras. Compare the bud with the 

 parent hydra as to size, form and number and size of ten- 

 tacles. Notice whether the bud moves independently or 

 only with the parent. When does it separate from the 

 parent ? 



9. In hydras collected late in the fall you may see another method 

 of reproduction. If such material is at hand, notice small swellings 

 near the proximal end and others near the tentacles. Eggs are pro- 



