330 PRINCIPLES OF SOIL MICROBIOLOGY 



stantly in the soil in sufficient numbers to admit the application of statis- 

 tical methods to the results. These are: (1) Dimastigamoeba gruberi, 

 (2) a small limax amoeba, (3) Heteromita sp. resembling Bodo repens, 

 (4) a small soil flagellate, 3 to 6 by 2 to 3^; (5) Cercomonas sp. and (6) 

 Oicomonas termo. Sandon found the following average number of 

 species of protozoa in 107 soils examined: 7.2 flagellates, 3.4 ciliates, 

 2.45 amoebae and 2.0 testaceous rhizopods. While some species de- 

 velop in all media employed, other forms develop only upon certain 

 specific media. 



In all Sandon 81 recorded 250 species of protozoa, a small number of 

 which were found in every soil, often in very large numbers. The 

 flagellates Heteromita globosus, Oicomonas termo and Cercomonas sp., 

 the ciliates Colpoda cucullus and C. steinii, and the limax amoebae 

 Ndegleria gruberi and Hartmanella hyalina were most common and 

 most abundant. While most protozoa found in the soil are also found 

 in various other habitats, such as standing and flowing fresh waters, sea 

 water, plankton, etc., a few are found only in the soil. 



The genera and species of protozoa vary with locality and degree of 

 soil cultivation. Fantham and Taylor 80 found 1 to 22 species in each of 

 a series of South African soils ; the flagellates were largest in total num- 

 bers, while the ciliates showed the largest number of species; the amount 

 of organic matter being the limiting factor; dark, heavy, humus rich 

 soils contained more protozoa than sandy soils; the reaction of the soil 

 was not found to have any effect upon the protozoan fauna. Sandon 

 has shown that the extreme climate of arctic land is no;t in itself an 

 obstacle to the abundant development of protozoa, provided the soil 

 is well manured and in good condition; however, peat soils are decidedly 

 unfavorable for the development of protozoa except for the testaceous 

 forms. A close positive connection has also been observed 78,81 between 

 the numbers of protozoan species and bacteria in the soil. 



The protozoa reported to have been found in the soil can be classified 

 as follows: 82 



82 The following letters can be used to designate the names of the investi- 

 gators, who have demonstrated the presence of the specific protozoa in the soil: 

 A — Wolff in Germany, B — France in Germany, C — Goodey in England, D — Martin 

 or Martin and Lewin in England, E — Waksman in New Jersey, U. S. A., F — 

 Fellers and Allison in New Jersey, U. S. A., G — Cutler, Sandon and Crump in 

 England, H — Cutler and Sandon in Spitzbergen soils, etc., I — Fantham and 

 associates in South African soils, J — Sandon working with soils collected through- 

 out the world, K — Yakimoff and Zcren in Russia, L — Perey 87 in France, M — 

 Allison 88 in England using American soils, N — Nowikoff in Russia. 



