450 



Mr. T. Goodey. Investigations on Protozoa in 



produced this change in one of them without killing off' the amoebae and the 

 flagellates. 



The Geescroft soil remained undried and has a much scantier protozoan 

 fauna than the Broadbalk 1865 soil, yet the curve for the bacterial counts in 

 this soil would be interpreted as showing the presence of the usual limiting 

 factor. 



I have no evidence on which to base a suggestion as to what the real 

 character of the change is which has been produced in the Broadbalk soils 

 by drying. I do suggest, however, that it has an intimate relation to the 

 high bacterial counts which I have obtained on remoistening the soils. 

 I am quite prepared to admit that the merely negative evidence furnished 

 by the above results does not help forward very much the final solution of 

 this elusive problem, but at the same time I think that it is useful. It 

 points to the fact that much more information is required than is at present 

 available on the changes brought about in soil by rapid air- drying or by 

 drying at temperatures sufficiently low to avoid the killing of protozoa in 

 the soil. 



Russell and Hutchinson give details of several experiments on this 

 particular line of investigation in their second paper (p. 166), but there is 

 room for still more research on these points. 



Hoosfielcl Inoculated Soil Bacterial Counts. 



The results of the bacterial counts for this set of soil samples are tabulated 

 below, and the curves obtained by plotting these are shown in figs. 6, 7, 

 and 8. As in the case of the 1846 set of soils I have arranged certain 

 curves together for the sake of simplifying matters. 



It is necessary to point out at the outset that in attempting to interpret 

 these results there are two standards of comparison, viz., the curve for the 

 untreated soil and that for the toluened soil. For this reason I have intro- 

 duced each of these curves into all three graphs. ' 



Fig. 6 shows the curves for the Untreated, Toluened, T. + Ciliates, 

 T. + Amoebae, and T. + Flagellates. It will be seen that the untreated soil 

 exhibits a normal low bacterial content ; the limiting factor is here exerting 

 its full influence. Compared with the untreated, the curve for the toluened 

 soil shows that the usual partial sterilisation effect has been obtained, the 

 bacterial numbers rising to and maintaining a level at about 50,000,000 or 

 60,000,000 bacteria per gramme. Examining now the curves of the three 

 inoculated soils represented in this graph and comparing them especially 

 with the curve for the toluened soil, we find that after the lapse of 487 days 

 the bacterial contents are higher than that of the toluened soil. Leaving 



