ADAPTATION FOR PROTECTION FROM ENEMIES 91 



necessary in its structure to offset the loss of an exoskele- 

 ton? 



4. A COMPARATIVE STUDY OF MOLLUSCA 



Materials. 



Specimens of as many different kinds of mollusks as 

 possible, charts, books. 



Observations. 



1. What is the symmetry ? ^ 



2. Is the body segmented or unsegmented ? 



3. Are lateral appendages present or wanting ? 



4. Is an exoskeleton present or wanting ? If present, 

 is it univalve or bivalve; if absent, what other means of 

 protection has been developed to take its place ? 



5. Is the animal fixed, or is it free to move ? If fixed, 

 in what way ? If it moves, what is the method and organ 

 of locomotion ? 



6. What are the organs of respiration ? What is their 

 character ? 



7. How is food obtained ? 



8. What senses are probably present? What sense 

 organs are present ? 



9. What is the habitat ? 



10. In what ways if any does the animal show degenera- 

 tion ? 



Summary. 



1. What characters are common to all mollusks ? 



2. What is the principal means of protection among 

 mollusks ? 



3. Name three causes of degeneration among mollusks. 



iThis and the following questions are to be answered for each 

 specimen. The answers may be tabulated if desired. 



