50 



PRINCIPLES OF SOIL MICROBIOLOGY 



Crump 119 estimated at frequent intervals the numbers of active pro- 

 tozoa and cysts in Rothamsted soils and found them to be much higher 

 on the manured than on the unmanured plot. 



The numbers of protozoa and bacteria were found to vary from day 

 to day. 120 An inverse relation was found between the number of active 

 amoebae and bacteria. 



The numbers of algae in the soil can also be determined by the dilu- 

 tion method, using the specific media, described elsewhere (p. 221) best 



Days 1 



Fig. 7. Daily variation of active flagellates in the soil (from Cutler and 

 Crump). 



adapted to the development of these organisms. 121 The numbers of 

 nematodes and other worms, insects and other members of the inverte- 

 brate population of the soil, as well as methods of determination, are 

 given elsewhere (p. 342). 



119 Cutler, D. W., and Crump, L. M. Daily periodicity in the numbers of active 

 soil flagellates : with a brief note on the relation of trophic amoebae and bacterial 

 numbers. Ann. Appl. Biol. 7: 11-24. 1920. 



120 Cutler et al., 1922 (p. 32). 

 111 Bristol-Roach, 1926 (p 225V 



