88 A GUIDE FOR THE STUDY OF ANIMALS 



a lens. What do you notice ? If your aquarium in which 

 the pond snail is living has a green coating ( algae) on the 

 side, describe its appearance after the snail has been crawl- 

 ing up and down over it. Explain. 



3. How many tentacles has a pond snail .' a land 

 snail ? Where are the eyes located in each case ? What 

 movements of the tentacles do you notice ? What is their 

 purpose ? 



4. How does the rate of locomotion of the snail compare 

 with that of the clam ? Find out if the snail can creep 

 backwards or on the surface of the water. Does there 

 seem to be any tendency for the snail to go up and down 

 the sides of the aquaria vertically rather than to the right 

 or left ? 



5. What does a snail do when disturbed .' What is 

 gained by this action .' 



, 6. Search for pond-snail's eggs on the side of the aquaria. 

 Lift up the bits of cabbage on which the slugs are feeding 

 and search for eggs. Describe what you find in each case, 

 noting the size, appearance, and whether the eggs are laid 

 singly or in masses. 



7. Find the breathing pore. Describe its position and 

 appearance. 



8. Contrast the various types of shells, and note with 

 care in what respects they differ. Holding the shell with 

 the aperture toward you and the spire pointing down, deter- 

 mine whether each shell has the aperture on the right 

 (right-handed shell) or on the left (left-handed shell). 

 Is the right-handed or the left-handed shell more com- 

 mon.' 



9. (Optional) By means of some book in the laboratory, 

 determine the scientific name of each of the snails found 

 in the various aquaria in the laboratory. 



