RELATION OF PROTOZOA TO SOIL BACTERIA 433 



hours before. He concluded that if these organisms had been 

 in the soil in an active state they would have possessed food 

 vacuoles, as these develop soon after the protozoan begins to 

 ingest its food. 



CONCLUSIONS 



In conclusion it maj^ be said that in the soil cultures the 

 presence of protozoa under the conditions of the experiments 

 did not have any noticeable effect, detrimental or otherwise, 

 on the processes of ammonification, nitrification and free nitro- 

 gen fixation. In the case of the liquid cultures employed in 

 the study of free nitrogen fixation the conditions w^ere at an 

 optimum for the development of the protozoa and under these 

 circumstances they limited bacterial activity as evidenced by 

 the harmful effect on the fixation of free nitrogen. Undoubtedly 

 under these conditions the protozoa were active in destroying 

 the Azotobacter cells. But in the soil cultures conditions were 

 evidently not favorable for the activity of the protozoa as these 

 organisms did not appear to exert any harmful influence on the 

 three soil processes studied. 



REFERENCES 



Cunningham, A. 1915 Studies on soil protozoa. Centbl. f. Bakt. (etc.) 

 Abt. II. 42, 8-27. 



GooDEY, T. 1911 A contribution to our knowledge of the protozoa of the 

 soil. Proc. Roy. Soc. (London), Ser. B., 84, No. B570, 165-180. 



Grieg-Smith, R. 1912 The inactivity of soil protozoa. Proc. Linn. Soc. 

 N. S. Wales. (1912), 655-672. 



LiPMAN, J. G., Blair, A. W., Owen, I. L., and McLean, H. C. 1910 Experi- 

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Russell, E. J. and Hutchinson, H. B. 1909 The effect of partial steriliza- 

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1913 The effect of partial sterilization of soil on the production of 

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Sherman, J. M. 1914 The number and growth of protozoa in soil. Centbl. 

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1916 Studies on soil protozoa and their relation to the bacterial flora. 

 Jour. Bact., 1, 35-66; 165-185. 



