ADAPTATION FOR PROTECTION FROM ENEMIES 89 



Suggested drawings. 



a. Drawings to show the pond snail in various positions 

 in the aquarium. 



b. A drawing of the slug. 



c. At least three different types of snail shell. 



Summary. 



1. In what respects does a snail show resemblance to a 

 clam .' 



2. What are the chief points of difference } 



3. What reasons can you suggest for the better develop- 

 ment of the sense organs ? 



4. What advantage has a snail over a clam in the mat- 

 ter of getting food .' 



5. How does the shell of the snail compare with that of 

 the clam as an organ for protection .' 



3. THE SQUID — A TYPE OF MOLLUSCA 



To show the Effect of a Much Reduced or Rudimentary 



Skeleton 

 Materials. 



Small squids, and a few large specimens for comparison 

 and dissection. 



Definitions. 



Cephalopoda, the name of the class to which the squid 

 belongs. 



Caudal fin, a. horizontal structure at the posterior end of 

 the squid. 



Chromatophores, irregular cells in the mantle which give 

 color to the squid. 



Exhalent siphon, a funnel or tube opening on the ventral 

 side just below the base of the arms or tentacles. 



