308 Dr. T. Goodey. Further Observations on 



point below the level of the (T + W) curve. The (T + F) curve reaches a 

 high level at 23 days, but not so high as that attained by the (T + C) and 

 (T + M) curves, and this is maintained at 78 days. After this it drops 

 rapidly, and at 154 days is well below the level of the (T + W) curve, a 

 position it maintains onwards to the end. The rise shown by all the curves 

 at 243 days is explicable, owing to the re-moistening of the soils. 



These curves are very similar to some of those dealt with in my previous 

 communication,* as in figs. 1, 2, and 6. 



The very high bacterial numbers attained in the (T + C), (T + M), and 

 (T + F) soils are to be accounted for, I believe, by the same explanation as 

 that put forward for the similar high counts in the earlier work, viz., that 

 by the addition of hay-infusion to the treated soil the bacteria of the soil 

 are given large quantities of food upon which they thrive and multiply 

 enormously, and that as these supplies of food become used up the numbers 

 of bacteria fall. 



The curves for the (T + C) and (T + M) soils are very much alike, and 

 one can say without hesitation that the same influences have been at work 

 in each case. The interesting fact also emerges from the consideration of 

 these two curves, namely that the elimination of the vast majority of the 

 bacteria by the electrical method described above has not had the effect 

 of decreasing the bacterial content of the (T + C) soil as might have been 

 expected; on the contrary, the (T + C) count at 21 days is slightly higher 

 than the (T + M) count. 



The protozoal counts for these soils are shown in the following Table in 

 approximate numbers per gramme of soil : — 





T + C. 

 Nos. per gramme. 



T + M. 



N03. per gramme. 



T + F. 

 Nos. per gramme. 



At start. 



Towards 

 end. 



At start. 



Towards 

 end. 



At start. 



Towards 

 end. 



Ciliates — 



Colpoda cucullus 



Tleurotricha sp. ? ... 

 Ehizopods — 



Amozba terricola ... 



1,000 

 30 

 50 



3,000 



10,000 



500 

 ? a few 

 ? a few 



20,000 



10,000 



1,000 

 30 

 100 



20,000 

 2,000 

 5,000 



1,000 

 ? a few 

 ? a few 



20,000 

 2,000 

 5,000 



1,000 

 1,000 



1,000 

 1,000 



The folowing ciliates occurred in cultures of the (T + M) soil so irregularly that no approxi- 

 mate estimate of their numbers could be formed ; only a few of each species were present per 

 gramme of soil : Colpoda steinii, Chilodon sp. ? JEnchelys sp. ? and 'Epistylis sp. ? 



* ' Boy. Soc. Proc.,' B, vol. 88 (1915 1 ). 



