i8 7 



If the tap-water was replaced by distilled water, the production of dry organic 

 substance was commonly smaller, which cannot, however, result from the nutrition 

 by substances in the tap-water, oxidisable by kaliumpermanganate, for the i4mgrs. 

 of permanganate, which our tap-water consumed per litre, we found quantitatively 

 back, at the end of the cultivation period, in the clear liquid beneath the pellicle of 

 B. oligocarbophiles, which liquid can easily be sucked off with a pipette, without any 

 considerable bacterial contamination. Moreover the experiments with distilled water 

 have likewise exhibited great divergency in production, and though the cause has not 

 been established with perfect certainty, we still think it probable, that these differences 

 result from the greater or smaller density of the cotton plugs, by which the speed 

 of air entrance is greatly influenced. We base this supposition on results obtained 

 with flasks, only differing in the width of the mouths, and to which we 'shall refer 

 later. It is furthermore certain that we have not to do here with the infection of 

 other bacteria, or with monads, for the pure cultures displayed as considerable diver- 

 gency as the crude ones. Neither can the chief cause be attributed to a change in 

 percentage of the air in gaseous carbon compounds, the differences being observed 

 simultaneously in cultures placed side by side in the same locality. 

 But we now give some further numbers. In an experiment with: 



Distilled water 100 



KvHPCU 0.02 



KNO 2 o.i 



KG o.oi 



Mineral solution* r drop 



sterilised and inoculated with a pure culture of B. oligocarbophilus, were found, after 

 37 days' cultivation. (2 Jan. 19 Febr.) at 23 C., 66.6 mgrs. of permanganate, corres- 

 ponding with circa 133 mgrs. of dry bacterial substance per litre. 

 In another experiment with: 



Distilled water 100 



Na 2 HPO4 0.02 



KNO2 o.oi 



Mineral solution* i drop 



likewise sterilised and after a culture of 40 days, at 23 C. the permanganate number 

 amounted to 60 mgs., corresponding with 120 mgrs. of dry bacterial matter per litre. 



In a third case in: 



i 

 Distilled water 100 



K 2 HPO-t 0.02 



(NHi)2S04 0.02 



NasCOs o.oi 



Mineral solution* 2 drops 



after cultivating from 5 May to i Dec., 155 mgrs. of permanganate per litre were 

 found. 



In a culture in: Distilled water 100 



Na2 HPOi 0.02 



KC1 0.02 



KNOs 0.02 



Mineral solution* i drop 



