380 



THE AMERICAN MONTHLY 



[Dec, 



Amoeba. 

 Actinophrys. 



Codonella. 

 Cryptomonas. 

 Dinobryou. 

 Mallomonas. 



KHIZOPODA. 



4.0 Difflugia. 

 3.0 



INFUSORIA. 

 6.0 Peridiniura. 

 1.0 Synura. 

 0.5 TintinDidium. 

 1.0 Trachoelmonas. 



7.0 



3.5 



2.0 to 10.0 



7.5 



1.0 



In order to show the difference between the Unit 

 Method and the old method of counting, the accompany- 



ing plate was prepared. The profiles were drawn from 

 the analyses of the Massachusetts State Board of Health. 

 Ludlow Reservoir, Springfield, and Haynes Reservoir, 

 Leominster, were selected because they showed great 

 seasonal variations in the number and kind of organisms. 

 The full line shows the number of organisms per c. c. as 

 given in the report. The broken line represents the 



