328 PRINCIPLES OF SOIL MICROBIOLOGY 



an abundance of ciliates and flagellates and few amoebae, 61 others 62 

 found amoebae and thecamoebae most prevalent. The discrepancy may 

 be due to the difference in methods used, especially in view of the sensi- 

 tiveness of the latter two groups to the composition of the medium. 

 Water appears to be the most important controlling factor, favoring the 

 development of the soil fauna. 63 The largest numbers of protozoa are 

 found in the soil in spring, after the thawing of snow or in summer, 

 after heavy rainfall; only cysts are found in dry and semi moist soils. 64 

 According to Crump, the protozoan fauna is largely confined to the top 

 six inches of soil. The amoebae are influenced by variations in the water 

 content and temperature of the soil and by the rainfall. The richer 

 the soil is in organic matter the richer it is in protozoa, especially in 

 amoebae and thecamoebae. A detailed study has been made of the 

 presence of protozoa in peat soils, 65 in Egyptian soils, 66 in Italian soils, 67 

 in German soils, 68 in the soils of the United States, 69 in Russian soils, 70 

 and in English soils; 71 an abundant fauna was found in various samples 

 of moss and soil from Spitzbergen and in soils of various South Sea 

 and Atlantic islands (Tristan da Cunha, Gough Islands, etc.). 72 Most 



61 Feuilletau and de Bruyn, W. K. H. t)ber die Verbreitung von Boden- 

 protozoen in den Alpen. Centrbl. Bakt. II, 56: 12-13. 1922. 



62 Crump, L. M. Numbers of protozoa in certain Rothamsted soils. Jour. 

 Agr. Sci., 10: 182-198. 1920. 



63 Coppa, A. Ricerche sui protozoi dei terreni delle acque ticinesit. Staz. 

 sper. Agrar. ital., 54: 181-213. 1921. 



64 Nowikoff, M. Die Bodenprotozoen und ihre Bedeutung fur die Bodenkultur. 

 Heidelberg. 1923. C. Winter. 



66 Scheffelt, E. Die Einzeller der siiddeutschen Moore. Mikrokosmos, 15: 

 113-118. 1922. 



66 Ross, R., and Thomson, D. Egyptian sand amoebae. Proc. Soc. Med., 

 Sect. Epidem., 9: 33. 1916. 



67 Cauda, A., and Sangiorgi, G. Untersuchungen iiber die Mikrofauna der 

 Boden aus Reisgegenden. Centrbl. Bakt. II, 42: 393-398. 1914. 



08 Wolff, 1912 (p. 329) ; Oehler, 1916-1919 (p. 319). 



69 Kopeloff, N., Lint, C, and Coleman, D. A. A review of investigations in 

 soil protozoa and soil sterilization (complete bibliography up to 1917). Soil 

 Sci., 3: 197-269. 1917. Fellers and Allison, 1918 (p. 326). 



70 Yakimoff, M. L., and Zeren, S. Contribution a l'etude des protozoaires 

 des sols de Russie. Centrbl. Bakt. II, 63: 33-57. 1924; Nowikoff, 1923. 



"Goodey, 1911-1915 (p. 323); Martin and Lewin, 1914-1915 (p. 318); Cutler 

 and Crump, 1920 (p. 50); Sandon, 1927 (p. 329). 



72 Sandon, H. Some protozoa from the soils and mosses of Spitzbergen. 

 Linn. Soc. Jour., 35: 449-475. 1924; Sandon, H., and Cutler, D. W. Some pro- 

 tozoa from the soils collected by the "Quest" Expedition. Linn. Soc. Jour., 

 36: 1-12. 1924. 



