16 Periodicity in Active Numbers of Soil Flagellates 



The regularity of the alternation is evidence of the reliability of our 

 methods ; for it is almost impossible to believe in an experimental error 

 having so constant and so distinct a rhythm. 



The possible sources of error are: 



1. Method of counting. 



2. Uneven distribution of protozoa in the field. 



3. The death of cysts as well as of active protozoa by the use of 

 2 per cent. HC1. 



Method of Counting. The paper in which this method is described (0) 

 gives proof of its accuracy; a few further examples may, however, be 

 given. 



Table II. 



