54 A GUIDE FOR THE STUDY OF ANIMALS 



respect are they plant-like ? What made students finally 

 class them as animals ? 



3. How do sponges reproduce? How are they dis- 

 tributed to new locations ? 



4. Where, as to depth of water, do most sponges grow ? 

 Where, as to oceans ? Where, as to latitude ? 



5. What are some of the difficulties which confront a 

 stationary animal ? How are they overcome ? 



6. To what class of sponges do the " toilet " sponges 

 belong ? Why ? 



7. What conditions are necessary for toilet sponges to 

 thrive ? Where are the best ones found ? Where are they 

 most numerous ? How are they collected ? How are they 

 prepared for market ? 



8. What is man able to do toward raising good sponges 

 for market ? 



9. Using reference books and museum specimens, de- 

 scribe some especially odd sponges. 



3. A STUDY OF C(ELENTERATES 



To show cells working together more definitely than in 



Sponges 



Materials. ^ Study of Hydra 



Living hydras in permanent aquaria, undisturbed. Liv- 

 ing hydras in small aquaria, i.e. tumblers, test tubes, watch 

 glasses, etc., with pieces of water weed and if possible some 

 of the microscopic animals found in water where hydras 

 are abundant. If kept cool, hydras may live several days 

 in such aquaria. Permanent slides of hydras ; some whole, 

 some in sections, and some showing the organs of repro- 

 duction. 



