40 







MOSKVA RIVER 

 STA TIONS 



PR EGO LY A RIVER 

 STA TIONS 



1\ 



N 



J I \ I \ \ L 



o 



2 4 6 



BIOTIC INDEX 



8 



Figure 2. Correlation between Woodiwiss' biotic index and bichromate 



oxygen consumption. 



146 



