FIG. 47 MONTHLY AVERAGES OF NUMBERS OF DIATOMS AND PROTOZOANS PER inin^ 

 AT SAFE HARBOR AND CONTROL STATIONS. 



-^91° *12 



lOB 



Each radius is numbered as the hours on a watch and represents that 

 month. Values are read from the center to the circumference. 

 A stations represent - 500 individuals /mm^ , B stations - 200 

 individuals /ram^ . 



115 



