G4 



Studies on Soil Protozon 



Table 12. Bacterial Content of solution before division = 2-6. 



F = flagellates. C — ciliates. A = amoebae. 



After 10 days a clearing in the .saponin solution set in which, taken 

 ill conjunction with the great increase in the bacterial content, appears 

 to point to the decomposition of the saponin. Tn order to test this 

 two equal quantities of filtered 1 % bloodmeal solution |- K2HPO4, 

 one of which contained -5 % saponin, were each inoculated with 1 c.c. 

 of a protozoa-free culture of bacteria. Bacterial counts were made 

 at the intervals shown in Table 13. 



From the results here obtained it is very probable that the bacteria 

 attack the saponin and that the resulting increase in bacterial numbers 

 will exaggerate the destructive effect of the protozoa. A second 

 disadvantage in the use of saponin is that at a concentration of -.5 % 

 it does not entirely suppress the protozoa. Higher concentrations have 

 been tried but up to 3 % one can never be certain that the whole of the 



