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Glass jars which have replaced polyethylene vessels used in bioassay of 

 pesticides. Four to six concentrations of each compound are tested simul- 

 taneously. Jars at left are used for fish, each holding 40 liters of medium 

 and 10 specimens. Because of canibalism, shrimp and crabs require isola- 

 tion. Individual animals are held in 4 liters of medium in smaller containers 

 (right), 10 being required for each concentration tested. 



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