CHAPTER VII. 



MOLLUSCA. 

 FIELD STUDY OF FRESH-WATER CLAM. 



LOOK for clams in the shallow water of creeks and lakes. Note 

 the natural position. How much of the shell is embedded ? Is the 

 shell open or shut ? Can you see any openings by means of which 

 the clam communicates with the water ? Touch the clam and 

 note any changes that take place. Quickly pull up the clam and 

 note the extended foot. Watch clams to see if they move. Do 

 they move with the same end always foremost? How does 

 the foot point with reference to the direction of locomotion? 

 Does a clam make a track ? Can you tell by the track in which 

 direction the clam traveled? Does the direction of travel have 

 any relation to the current of the stream? Why do clams 

 travel? If possible, make a series of observations to find out the 

 rate of locomotion. Where are clams more abundant, on sandy or 

 on muddy bottoms ? How many kinds do you find ? Do differ- 

 ent kinds show preference as to soil ? Has the color of clams 

 any relation to the surroundings? Do you find any evidence that 

 clams have enemies? Of what kinds? How are clams protected 

 from enemies? What conditions are unfavorable to clams? Do 

 they prefer deep or shallow water? Do they occur singly or in 

 groups? Do different kinds occupy the same region? 



AQUARIUM STUDY OF A LIVE CLAM. 



If a good aquarium is not obtainable, a battery jar, a tub, or a 

 large pail will serve. Put in three inches of sand and add enough 

 water to stand three inches above the sand. Let this stand ov( 

 night to allow the water to become clear. 



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