Report on the Bacteriology of Water. 

 Bichromate. 



379 



Curve 73, p. 378. 



Doubling periods : 



1. 13 -5 27 fi = 2.30 P.M. 2.42 P.M. = 12 minutes at 22 -923 -122 -5 C. 



2. 27-0 54 = 2.42 3.17 =35 22 -521 -5 C. 



3. 54 -0108 = 3.17 4.7 =50 21 -5-23 '021 '0C. 



4. 108 -0216 = 4.7 5.9 = 62 21 -019 '3 C. 



It is pretty evident, in spite of the irregular and almost abnormally 

 rapid growth recorded for the bichromate culture at first, that a 

 prolonged retardation occurred in the water culture a retardation 

 which, for broth cultures, is too long for the temperatures, and can 

 only be referred to the light. 



On November 16 I sowed spores in normal 10 per cent, gelatine, 

 and put into 22 C. at 10 A.M. Two cultures were made, and at 12.30 

 these were exposed as follows, to test the effect of the light from a 

 blue sky on germinating rodlets. The two cultures stood side by 

 side on a mirror, each covered with a matchbox screen ; on one lay 

 a blue glass, and on the other a red one. The sky was fairly clear, 

 but clouds passed occasionally. 



Two control-cells with thermometers lay beside them, and each of 

 these was arranged exactly like its culture, the glasses used for 

 screens being in each case the half of the same piece of glass as that 

 on the culture. 



The temperature was rather low, and ran as follows during the 

 exposure from 12.30 to 4 P.M., on west side of laboratory, and com- 

 pletely sheltered from any direct sunlight. 





2 D 2 



