40 JAMES M. SHERMAN 



Outline of work undertaken 



Preliminary to any work on the part played by the soil pro- 

 tozoa, two essential points should be established: (1) whether 

 protozoa occur in soil in numbers sufficient to be a factor in soil 

 fertility; and (2) whether protozoa lead a trophic life in the 

 soil. Unless these two points can be settled in the affirmative, 

 it would appear that discussions concerning the role played 

 by the micro-fauna of the soil must be considered more or less 

 futile. The first part of this work was therefore directed toward 

 getting more definite information as to the number of protozoa in 

 soil and the nature of their existence therein. 



A study was made of the effect of protozoa upon the bac- 

 terial flora of the soil by the isolation of animal-pure cultures 

 of some representative soil protozoa and inoculation into 

 protozoa-free cultures of soil bacteria, in solutions and in soil, 

 and also by the comparison of the activities of bacteria in 

 sterilized soil reinoculated with normal soil and with ''protozoa- 

 free soil." 



The last part of the work was devoted to a study of the action 

 of volatile antiseptics in soil in an effort to throw some light on 

 the part played by the protozoa. 



II. THE NUMBER OF PROTOZOA IN SOIL 



Present status 



Although the soil protozoa have attracted considerable atten- 

 tion in recent years, few data are at hand showing the number of 

 such organisms actually found in normal soils. Stormer (1907) 

 showed that fertile soils sometimes contain several thousand 

 amoebae per gram as determined by the agar plate method of 

 enumeration. Hiltner (1907) reported the finding of large num- 

 bers of protozoa in soil, and said that flagellates and amoebae 

 had been found in numbers reaching millions per gram. He did 

 not report the specific data upon which this statement was based, 

 nor did he give the details of the method by which the numbers 

 of protozoa were determined. Lodge and Smith (1912), on the 



