STUDIES ON SOIL PROTOZOA 



53 



before the pots were put out of doors and at the end of 45 days 

 and 105 days periods outside. The data obtained are presented 

 in Table VIII. 



If the soil protozoa have a detrimental effect upon the bac- 

 teria we should expect the number of bacteria in the pots inocu- 

 lated with ordinary soil to rise very markedly, while in the soils 

 free of protozoa there should not be such an increase. There 

 was, apparently, no difference in the behavior of the bacteria 

 in the different soils. 



TABLE VIII 



Effect of low temperature upon the number of bacteria in soils containing protozoa 



arid free of protozoa 

 Before being placed out doors 



Forty-five days after being placed out doors 



250,000,000 

 270,000,000 



260,000,000 



130,000,000 

 60,000,000 



95,000,000 



One hundred and five days after being placed out doors 



280,000,000 

 336,000,000 



308,000,000 



100,000,000 

 120,000,000 



110,000,000 



Another experiment was performed on the relation of tempera- 

 ture to the bacterial flora in the presence and absence of pro- 

 tozoa. Three pots of sterile soil were inoculated with normal 

 soil while three other pots were inoculated with the protozoa- 

 free soil. One pot of the soil from each lot was then incubated 

 at each of three temperatures, 10°C., 22°C., and 37°C. for a 

 period of 30 days. In this case also there should be a difference 

 in the development of the bacteria in the two soils at the various 

 temperatures if soil is possessed of a detrimental biological factor. 

 The results (Table IX), as in the foregoing experiment, give no 

 evidence of a phagocytic agent. 



