86 A GUIDE FOR THE STUDY OF ANIMALS 



8. Note the texture of the mantle. How many lobes 

 has it ? What is their extent ? How are the lobes related 

 to the valves ? 



9. Remove or lift up one mantle lobe. Identify the soft 

 body, the foot, the gills, the palps, and the mouth. Which 

 of these structures are arranged in pairs ? 



10. Determine the structure and composition of the shell 

 as follows : — 



a. Break a thick clamshell and examine ^ the broken 

 edge. Identify the inner or pearly layer and the outer or 

 chalky layers. What gives color to the shell in the living 

 clam } 



b. Burn a small piece of shell in an evaporating dish 

 over a bunsen burner. What is the appearance of the 

 shell after burning.' What has been burned, animal or 

 mineral matter .-' What then is the residue 1 



c. Place a small piece of shell in acid. What results ? 

 Is there a large amount of residue .? What constitutes the 

 greater part of the shell, animal or mineral matter ? 



d. (Optional) Devise some method and determine the 

 approximate per cent of mineral and of animal matter in 

 the clamshell. 



Summary. 



1. Why did we study the clam .' (See title of exercise.) 



2. How has the heavy shell of the clam affected : — 



a. The character of the clam's body, 



b. the locomotion, 



c. the development of sense organs. 



3. What special problems has the clam as regards get- 

 ting food and oxygen .'' How are these problems solved .' 



4. How does the clam protect the young clam during 

 development .' 



