Report on the Bacteriology of Water. 439 



Doubling (second normal doubling period) : 



54108 p = 7.42 P.M. 9.4 P.M. = 82 minutes at 21 '9 C. 

 108-216 = 9.4 10.31 =87 21 -9 21 '821 '9 C. 



The foregoing cultures and their growth-curves are extremely 

 interesting and instructive, especially because the temperatures were 

 fortunately so constant. 



As we see, the normal doubling period at 21*6 21*4 was sixty-one 

 minutes in the first case, where the germination period occupied five 

 and a quarter hours, but it was seventy-two minutes (at 2T75 21'9) 

 in the second case, with a germination period of five hours and a 

 shorter filament. The question arises, Why did the second culture 

 occupy eleven minutes longer in doubling its shorter filament, 

 although it had been exposed a quarter of an hour less time to the 

 22 C. of germination, and although the temperature was nearer the 

 optimum by 0'3 to 0'25 C. ? 



I think the explanation is that the temperatures further from the 

 optimum were brought to bear at an earlier stage on a relatively 

 weaker plant, and the latter therefore coped less ably with the more 

 unfavourable circumstances. 



Turning again to the second culture, it is worth noting that its 

 second normal doubling period, at perfectly constant temperature, be it 

 noted, is distinctly longer than its own first one eighty-two minutes 

 against seventy-two bearing out my previous remarks as to the 

 gradual slowing of growth as the culture ages, and, no doubt, due to 

 the slow exhaustion of the food-materials and fouling of the medium 

 by products of metabolism. 



On November 27 spores in normal gelatine were sow a at 2.15 and 

 put at 22 C. till 8.5 P.M. 



Doubling periods : 



114-5229-0 /x = 8.5 P.M. 8.55 P.M. = 50 minutes at 22 -7522 -25 C. 

 229-0 458-0 = 8.55 9.48 =53 22 '25 23 -0 C. 



Calculated back : 



454-5 227 '25 n = 8.55 P.M. 9.48 P.M.= 53 minutes at 22 -2523 -O c C. 

 227-25 113-75,, = 8.4 8.55 =51 22 '75 22 '25 C. 



Normal doubling period : 



176-0342-0 /x = 8.35 P.M. 9.27 P.M. = 52 minutes at 22-523 -0 0. 



Spores sown November 26 at 12.45 in normal gelatine at 22 C., 

 remained till 7.45 P.M. and were then measured at 23. 



