44 JAMES M. SHERMAN 



data, the ciliates do not ordinarily occur in numbers approxi- 

 mating 1,000 per gram. Colpoda cucullus which has been widely 

 noted as an inhabitant of soil, appears to be the most generall}^ 

 distributed ciliate. This organism may be very often, but not 

 constantly, found in 1/100 of a gram of soil. In one Virginia 

 soil (Table II), Balantiophorus elongatus was found in the 1/1,000 

 of a gram dilution. With the methods employed, it would not 

 be safe to draw any conclusions regarding the amoebae other 

 than that they do not occur in numbers nearly as great as do the 

 flagellates in ordinary soils. Although the culture media and 

 period of observation used are not adequate for work with the 

 amoebae, it is worthy of note that in the peat soil, containing a 

 high humus and water content (in which we should expect to 

 find numerous amoebae) the method was of sufficient service 

 to show their presence in 1/1,000 of a gram in one of the two 

 samples taken. In spite of the limitations of the methods used, 

 amoebae would probably have been revealed had they been of 

 general occurrence in large numbers. Using the same medium 

 and inoculating with a large amount of soil, amoebae have been 

 observed as early as the third day. 



In the dilutions of 1/10,000 of a gram, with one exception, 

 only four general types of protozoa have as yet been noted: 

 Monas sp. Dimorpha radiata (?) and two other flagellates which 

 have not been identified. 



III. THE GROWTH OF PROTOZOA IN SOIL 



Previous work 



In order to correlate the protozoa with any of the vital func- 

 tions of the soil, it is first necessary to demonstrate that they ai-e 

 active in soils of normal moisture content. Goodey (1911) made 

 a very careful study of the ciliates of the soil and concluded thjit 

 these organisms exist in soils of normal moisture content onh- 

 in the encysted condition. When free water was to be found 

 on the soil active protozoa could be demonstrated, but no active 

 ciliates could be detected in ordinary soils. Russell and Golding 

 (1912) working with water-logged, "sewage sick" soil, demon- 



