Report on the Bacteriology of Water. 311 



rates which are really enormous if we regard the relations of size. 

 This is the more marvellous when one notices that this rapidity of 

 growth was increasing although the temperature was falling the whole 

 time. 



This last is an important point, for if we now turn to the culture 

 in the light, we find nothing like such a general increase in the 

 power of development. Nevertheless, the filament clearly began to 

 grow much more rapidly after sun-down (see 5.47 and 6.1 P.M), and 

 was evidently tending towards some such maximum at 7.23. 



Now, why did not this filament begin to get up its maximum of 

 growth as soon as the other ? It was a lunger and more vigorous 

 specimen to begin with, for I purposely chose a germinal filament 

 25 ft long, whereas that in the dark was only 15 fi long and unless 

 Borne inhibiting agent was keeping it back, it seems incredible that 

 its general curve of growth should ascend so slowly before sun- 

 down. 



But it seemed clear that the inhibition cannot be due to the tem- 

 perature, because that was falling too slowly to produce such an effect; 

 and, besides, it falls practically equally in both cases, so that if it 

 checked the growth of this culture, one asks why the lowering of the 

 temperature did not check it in the dark ? 



If, then, the growth is accelerated after sun-down, in spite of a fall 

 of temperature as we see to be the case the logical conclusion 

 seemed to be that the acceleration is due to the withdrawal of the 

 inhibiting rays of light, and on the hypothesis that this is the case 

 the curves are intelligible. 



Germination and Growth behind Glass Screens. 



In view of the encouraging results of which the above is an illus- 

 tration, it appeared worth while to further test the action of light on 

 the germination and growth of this schizomycete, and this I did with 

 the following measure of success. 



The method employed was as follows : A quantity of dilute broth 

 in a test-tube was infected with the ripe spores to such an extent 

 that the smallest drop I could manipulate with a platinum loop con- 

 tained on the average at least about twelve and not more than about 

 twenty-five spores. 



I then made a number of hanging-drop cultures in the usual 

 manner, on thin, sterilised cover-slips, each being at once luted to the 

 moist chamber by means of sterile gelatine. 



Each moist chamber was then placed on a piece of glass, plain or 

 coloured, about 3.| inches square, and covered by a similar square of 

 tin; same glass, supported just above the cover-slip from which the 

 drop was suspended, by means of a suitable wooden block. 



