850 CONTRIBUTIONS TO OUR KNOWLEDGK OF SOIL-FERTILITY, xii. 



Conditions which cause the apparent destruction of the sulphur- 

 oxidising bacteria also cause the destruction of the ciliates. 

 This is much akin to the conclusion of Russell and his colleagues, 

 who say that conditions which preclude the presence of the 

 nitrifying bacteria, also preclude the presence of a mixed fauna. 

 While this does not appear to hold for the nitrifying bacteria 

 (see p. 845) of dry soils, one has to bear in mind that experiments 

 with the protozoa are always more or less variable. 



