PLATE II 



PLATE COUNTER (Modified from Jeffers). 

 For Counting CoiiONiES op Bacteria. 



The cross lines divide the figure into square centimeters. The 

 numbers indicate the area of the various discs. The area of each 

 sector (a. and b.) is one-tenth of the whole area. (See page 126.) 



Facing page 137. 



