SOIL ORGANISMS 387 



While nematodes, rotifers, and similar organisms are some- 

 times found in soil, the protozoa are the only important micro- 

 scopic animal group usually present. The importance of 

 protozoa in soils was especially emphasized in 1909 by Russell 

 and Hutchinson, 1 who maintained that the protozoan flora so 

 interfered with the ammonia-producing bacteria as materially 

 to lower the productivity of the soil. Partial sterilization 

 seemed to alleviate this condition, possibly by killing the 

 harmful protozoa. The findings of Russell and Hutchinson 

 have resulted in much research as to the importance of proto- 

 zoa in a normal soil. 



While Waksman 2 found that the presence of protozoa was 

 concomitant with low bacterial numbers, he does not consider 

 all protozoa harmful to biological activities. Fellers and Alli- 

 son, 3 in an examination of New Jersey soils, found protozoa in 

 every sample, the number of species ranging from two to 

 twenty-eight. Soils rich in organic matter or containing large 

 amounts of water carried the greater number. Besides the 

 104 species of protozoa identified in New Jersey soils, ten 

 genera of alga? and six of diatomes were isolated. Nematodes 

 were common. The number of protozoa ranged from a very 

 few to as high as 4500 to a gram of soil. When occurring in 

 such numbers, these animals must be of considerable impor- 



1 Russell, E. G., and Hutchinson, H. B., The Effect of Partial Sterili- 

 zation of Soil on the Production of Plant Food; Jour. Agri. Sci., Vol. 

 Ill, pp. 111-144, 1909. Also, The Effect of Partial Sterilisation of 

 Soil on the Production of Plant Food. II. The Limitation of Bac- 

 terial Numbers on Soils and Its Consequences; Jour. Agr. Sci., Vol. V, 

 part 2, pp. 152-221, 1913. 



a Waksman, S. A., Protozoa as Affecting Bacterial Activities in the 

 Soil; Soil Sci., Vol. II, No. 4, pp. 363-376, 1916. Also, Sherman, 

 J. M., Studies on Soil Protozoa and Their Relation to the Bacteria; 

 I. Jour. Back, Vol. 1, No. 1, pp. 35-66, 1916. II. Jour. Back, Vol. 1, 

 No. 2, pp. 165-184, 1916. 



Kopeloff, N., and Coleman, D. A., A Review of Investigations in 

 Soil Protozoa and Soil Sterilization; Soil Sci., Vol. Ill, No. 3, pp. 

 197-269, 1917. 



"Fellers, C. R., and Allison, F. E., The Protozoan Fauna of the 

 Soil of New Jersey; Soil Sci., Vol. IX, No. 1, pp. 1-24, 1920. 



