1920] 
ALLEN—CARBOHYDRATE CONSUMPTION BY AZOTOBACTER 79 
the rate of increase in cell numbers predicted by Duclaux for 
bacterial cultures in general. Indeed, the curves resemble the 
antipode of the Duclaux curve. 
It might be argued that the decrease in rate of sugar consump- 
tion with increase of time in the cultures is due to accumulation 
of by-products, and that this decreased activity corresponds to 
the falling away from the purely mathematical curve in older 
cultures, as discussed by Duclaux. The production of toxic 
substances within seven days in cultures as slow growing and as 
dilute as these seems to us to be unlikely. Moreover, the fact 
- that the cultures are able to utilize a second portion of sugar 
seems to us to be opposed to the idea of growth-inhibiting sub- 
stances in the medium. 
The results show also that the cultivation of the organism 
under the influence of mechanical agitation of a certain type 
influences to a marked extent the carbon assimilation in its time 
relations. 
On the whole, the experiment emphasizes the need for more 
studies on the periodic changes in the culture of this organism. 
In conclusion, the writer wishes to express his thanks to Pro- 
fessor P. A. Shaffer for rendering this work possible; to Professor 
B. M. Duggar for suggesting the method of attack, and to Mr. 
A. Bonazzi for suggestions in regard to the arrangement of the 
manuscript. 
LITERATURE 
Allen, E. R. (19). Some conditions affecting the growth and activities of Azoto- 
bacter chroococcum. Ann. Mo. Bot. Gard. 6: 1-44. 1919 
Bonazzi, A. (19). On nitrification. II. Intensive nitrification. Jour. Bact. 4: 
43-59. pl.1. f.1. 1919. 
Duclaux, E. (98-00). Traite de microbiologie. 1:208-212. 1898; Ibid. 2: 
60-75. 1900. 
