Report on the Bacteriology of Water. 



363 



The results are not so conclusive as in previous cases with blighter 

 light, but, so far as they go, they bear out the inference already 

 drawn, viz., that the light does inhibit the germination of the spores 

 even though it is very feeble so far as blue rays are concerned. 



The following experiment, carried out on June 30, a veiy hot day, 

 with a slight haze but no clouds in the blue sky, bears out the fore- 

 going conclusion that the action is due to intense destructive meta- 

 bolism at high temperatures (see p. 375). 



Spores were sown and exposed at 7 A.M., a more dilute gelatine, 

 5 per cent., with only traces of broth, being used. Control cultures 

 in the dark at 24 C. showed that germination and growth can go on 

 quite well in this medium, and filaments of 2CO to 250 /t were deve- 

 loped by 3 P.M. from these controls put into the incubator at 7 A.M. 



The temperatures reached were occasionally rather high, as the 

 following table shows, but the exposed cultures were subjected to 

 exactly the same influences, except as regards the light (never direct 

 from the sun) filtered through the screens. The arrangement was 



exactly as before. 



Temperatures. 



Time. 

 7 A.M. 



8-30 



11 



12 noon 

 12.30 P.M. 



3.30 

 9 . 



At 3.30 P.M. the bichromate culture showed several germinating 

 rodlets, and by 9 P.M. these had grown considerably. That the high 

 temperatures and great range had retarded them, however, even in the 

 orange light, was evident from the much better growth of the con- 

 trol cultures kept constant at 24 C. in the dark incubator. On 

 July 1 i.e., next day there were plenty of well-grown colonies, but 



2 C 2 



