By ft. GREIG-SMITM. 659 



Altliuugh living- protozoa were added to the soils of the tirst 

 set, the bacteria increased enormously in six days. A phagocytic 

 activity is not apparent. The subsequent decline may, hovi^ever, be 

 due to the ciliates, but it is more likely caused by the secretion of 

 toxins by the bacteria. The continued excess of bacteria, in the 

 test containing the living protozoa, in no way confirms the phago- 

 cytic hypothesis. Indeed, it is evident that the reason for the rapid 

 increase of the numbers, in the tirst test, w'as caused by the intro- 

 duction of a number of rapidly growing, feebly-resistant bac- 

 teria, which soon succumbed to the effect of their own toxin. The 

 resistant bacteria, being also more numerous, probably account for 

 the continuation of the greater number, as time went on. The 

 nature of the colonies upon the plates was instructive. Those 

 derived from the "living" soils were chiefly of the translucent-white 

 or yellowish glistening kind, characteristic of the coli-Jluorescens 

 group of bacteria, while those from the "dead" soils were mostly 

 opaque, white and granular, indicative of the subtilis-vulgatus 

 bacilli. The odour of the plates was also marked. Those of the 

 "living" set had a disagreeable, putrefactive smell, in sharp con- 

 trast with the faint odour of the other. By the twenty-seventh 

 day, the distinctive odours had disappeared, and the colonies were 

 very much the same in both tests. 



The suspensions had been tested for living protozoa by infecting 

 sterile 4% bean-infusions. The heated suspension contained none, 

 while the raw suspension gave rise to many. On the fourteenth 

 day, the soils were tested in a similar manner. Both contained 

 Colpoda, and the "living" soil contained amceba? in addition. Upon 

 testing the original chloroformed soil, it was discovered that the 

 protozoa were still alive; a luxui-iant growth of Colpoda cucullus 

 being obtained. Thus the treatment Avith 2% chloroform had not 

 been sufficient to destroy the encysted ciliates. 



For destroying protozoa, Russell and Golding used 2% of carbon 

 bisulphide or toluol, allowing it to act for two days; while, for 

 field-work, they suggest the emjjloyment of from two or three cwt. 

 per acre, as a suitable quantity. This is, roughly, the equivalent 

 of from 0-01 % to 0-02 %. llussell and Hutchinson used 4 % of 



