452 Mr. T. Goodey. Investigations on Protozoa in 



flagellates per gramme. These are large numbers of protozoa, and it is 

 probable that the amoebae and flagellates have occurred in the active 

 condition. In no case, however, have these protozoa been able to reduce 

 the bacterial contents of their respective soils to a level permanently below 

 that of the toluened soil. Cultures were made at the end of the experiment 

 to ascertain if protozoa were present in the toluened soil, with the result 

 that about 5000 flagellates and about 10 amoebse per gramme were found in 

 it. Now the curve for the toluened soil is quite a normal one, and shows 

 the usual partial sterilisation results when compared with that of the 

 untreated soil. 



Whatever be the limiting factor eliminated by the process of toluening 

 and heating this soil, resulting in the rise of the bacterial content from 

 10,000,000 or 12,000,000 to 50,000,000 or 60,000,000 bacteria per gramme, 

 that factor evidently has no connection with the flagellates, for these have 

 resisted the action of the antiseptic and heat and, though much reduced in 

 numbers at the beginning of the experiment, have succeeded in repopulating 

 the soil. 



The results obtained from these inoculated soils accord with those 

 obtained from inoculated samples of 1846 soil. In those it was found that 

 the ciliates, amoebse, and flagellates failed to reduce the bacterial content 

 below the level of the untreated soil. In this soil they have not brought 

 down the numbers of bacteria lower than those of the toluened soil. The 

 only inference which I can draw from these results is that the protozoa have 

 not functioned as the limiting factor on bacterial activity. 



The curve representing the counts for T. + Bacteria as compared with 

 those for the toluened and untreated soils is shown in fig. 7. It is 



208 256 



DAYS 



Fig. 7. 



