432 T. L. HILLS 



is furnished for the protozoa which is never met with in soils 

 under normal conditions. 



The results of the work at the New Jersey Experiment Station 

 are not in accord with Russell and Hutchinson's theory. Lip- 

 man et al. (1910) found that the protozoa do not play any im- 

 portant part in depressing the activity of the soil bacteria. This 

 was shown by a series of experiments performed relative to a 

 possible influence which the protozoa might have on the im- 

 portant soil process of ammonification. 



Concordant results have been obtained by Sherman (1916) 

 who worked with six species of protozoa, namely, the two ciliates 

 Colpoda cucullus and Balantiophorus elongatus, which are not 

 active in soil and four flagellates, which by test were shown to 

 be active in soil. The ciliates had a very marked detrimental 

 effect upon the number of bacteria in soil extract but had no 

 effect upon them in soil. Three of the flagellates had no effect 

 upon the number of bacteria either in soil extract or soil. The 

 fourth flagellate had a very marked detrimental effect in soil 

 extract but none in soil. These experiments were performed 

 many times and always with the same results. 



In an earlier work Sherman (1914) showed conclusively 

 that some protozoa can increase in numbers in the soil under 

 ordinary conditions but from the results of his later work it 

 is probably doubtful if they have any appreciable effect on limit- 

 ing the numbers of the soil bacteria. 



Grieg-Smith (1912), drawing conclusions from his own work, 

 thinks that the protozoa have but little effect on the bacteria 

 of the soil. He tested the action of the soil phagocytes (the 

 protozoa) in the same manner as Russell and Hutchinson did 

 and from his experiments he concluded "that Russell's conten- 

 tion cannot be sustained; the protozoa have little or no action 

 in limiting the number of soil bacteria." 



Goodey (1911), working with the ciliates only, thinks that 

 these protozoa do not exist in the soil in an active state, but 

 that they are present in an encysted condition. He made a 

 careful study of recently excysted Colpoda cucullus obtained 

 from soil which had been added to a suitable medium but a few 



