Report on the Bacteriology of Water. 



335 



I examined the culture-drops at 12.30, 3 o'clock, 5.15 P.M., 9 P.M., 

 and 11 P.M., taking note of the extremes and of the commonest 

 lengths of the germinal filaments developed, with the following 

 results (Curves 28 and 29, p. 337) : 



That the light and not the temperature was the effective agent in 

 delaying the germination of the spores between the blue glasses 

 hardly admits of any doubt after this experiment, the most 

 astounding thing about the matter being the prolonged action of the 

 inhibition effect ; for it was permissible to expect that when once the 

 germination had begun, the plantlets would rapidly gain strength 

 during the dark hours of the night. Such was not the case, how- 

 ever, and this fact certainly seems to support the idea that the action 

 is on something whether substance or machinery in the spore 

 itself, so that the plant produced is really a weakened organism 

 incapable of assimilating the nutritive substances of the food-medium 

 with anything like the normal vigour. 



Later on, it is true, the retarded blue culture' did slowly recover 



* Opened window for three minutes = all fell 5 to 6 C., but rose on closing 

 again. 



t On removing shutters from both dummies and turning mirror to sun, the 

 readings during consecutive minutes = 19, 21, 25, 28, 31 (for blue), and 24, 27, 

 31, 35, 38 (for red) ; they fell as rapidly on replacing shutter and taking light from 

 blue sky only. 



J On exposing full as possible to sun the red dummy rose to 40 41'5 in a few 

 minutes, the blue dummy to 39 40. They fell as quickly on replacing. When 

 fully shaded from all sunlight, both fell, in five minutes, to 22 > 5. 



