36 JAMES M. SHERMAN 



Within the past few years more attention has been directed 

 toward the soil protozoa with the result that they have been 

 demonstrated to be of general occurrence in the soils of those 

 parts of the world which have been studied. In England, Russell 

 and Hutchinson (1909) (1913), Russell and Golding (1912), 

 Goodey (1911), Martin (1912), and Martin and Lewin (1914) 

 have noted the constant presence of protozoa in soil. Similar 

 observations have been made by Wolff (1909) (1912), France 

 (1911), Killer (1913), Emmerrich, Leiningen and Loew (1912), 

 and Cunningham and Lohnis (1914) in Germany; by Lodge and 

 Smith (1912), Gainey (1912), Rahn (1913) and Sherman (1914) 

 in the United States; by Cauda and Sangiori (1914) in Italy, 

 Peck (1910) in Hawaii, and Greig-Smith (1912) in Australia; 

 while Loew (1911) (1913) has observed them in the Alps, in Porto 

 Rico, the Island of Borkum, and in Japan. Important contribu- 

 tions to our knowledge of the types of protozoa which occur in 

 soil have been made by Wolff (1909), France (1911), Goodey 

 (1911) (1914). IVIartin (1912), and Martin and Lewin (1914). 



The relation of protozoa to bacteria 



It is well known that bacteria constitute the chief food for 

 many types of protozoa. Many of the ciliates in particular are 

 especially destructive to bacteria, although this property is pos- 

 sessed by the other classes as well. Indeed, Calkins (1901) has 

 said that probably all protozoa ingest bacteria with the excep- 

 tion of the parasitic forms and those which live on other protozoa. 

 This view, however, has been modified considerably in recent 

 years and it is now known, as is stated by Minchin (1912), that 

 a number of protozoa are saprozoic in nature and obtain their 

 food by absorption. A considerable portion of the non-pai-asitic 

 flagellates belong to this class. 



In many places in nature bacterial development is limited by 

 the action of predatory protozoa. Huntemtiller (1905) and 

 Korshun (1907) have proven that the micro-fauna plays an 

 important part in the purification of water. The possibility 

 that protozoa are inimical to the soil bacteria has only very 



