92 A GUIDE FOR THE STUDY OF ANIMALS 



5. MOLLUSCA : REVIEW AND LIBRARY EXERCISE 



Characteristics. 



1. What are the general characteristics of mollusks ? 



2. Name the principal classes and give the characteris- 

 tics of each. 



Morphology. 



3. What is peculiar about the structure of a clam's 

 heart ? What is its position ? Contrast with the heart of 

 a crayfish. 



4. Make cross-sectional diagrams to show the arrange- 

 ment of parts in a clam : {a) in the region of the umbone ; 

 {b) in the region just in front of the posterior muscle; 

 (c) in the region of the anterior muscle. 



5. Describe the various types of eyes found in mollusks, 

 and their location. 



6. Describe the tongue or lingual ribbon of the snail, 

 and its use. 



7. What is the operculum of snails .' its use } 



Physiology. 



8. Describe the circulation of water through the siphons 

 and mantle cavity of a clam. How is it caused .' What 

 three uses has it .'' 



9. What are the principal facts about the development 

 of fresh-water clams ? 



10. Describe the circulation of blood in a clam. 



11. What various methods of locomotion are found 

 among moUusca .-' 



Economics. 



Write a short account of the following : — 



12. Oyster culture. 



13. Typhoid-fever and oysters. 



