THE BIOLOGICAL EELATIONS OF SOME 

 AQUATIC FORMS OF LIFE 



PROBLEM XXXIII (Optional) 



A study of mollusks and their enemies with special 

 reference to their economic importance. 



a. Relations 



Observations. 1. Fill in the following tabulation : 



Questions 



1. Why are stakes and brush sometimes sunk in shallow water in arti- 

 ficial oyster culture ? 



2. What is the source of sepia ? 



3. Where are the best pearl fisheries ? 



4. Where is the center of the pearl button industry in this country ? 



Special Reports 



1. The use of shells as money. 



2. The artificial pearl industry. 



3. The starfish in relation to mollusks. 



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