Report on the Bacteriology of Water. 453 



Normal doubling period : 



58-5117 -0 ft. = 3.40 P.M. 4.9 P.M. = 29 minutes at 35 -5 33-75 C. 

 40-5 81-0,, = 3.20 3.55 =35 32 35 '534 '3 C. 



Calculated back : 



141-7570 -8 n = 3.48 P.M. 4.15 P.M.= 27 minutes at 34' 5 33 '25 C. 



I.e., with a range of 3'5C. it took 35 minutes to double, whereas 

 with a range of 1'25 C. it only took 27 minutes. 



But we must scrutinise cautiously these results with varying high 

 temperatures acting on a culture in process of accommodation. 



At 4.28 another filament was selected, and this was showing the slight 

 but distinct writhing movements so often seen at high temperatures. 

 The movement was especially noticeable in a segment, about 20 /* 

 long, which was slowly bending backwards and forwards, and which 

 had broken off, when 22'5 /* long, at 4.50 : since it remained close to 

 the parent segment, however, it was easily measurable with it. 



This had to be abandoned now, the measurements becoming too 

 difficult. The rate of growth was fairly rapid, and the length was 

 doubled as follows : 



126252 M = 4.28 P.M. 5.4 P.M. = 36 minutes at 34 75353435 C. 



Which taken with the preceding shows that strong plants, once 

 germinated out, can stand these high temperatures (even varying) 

 very well for a time, though their growth is correspondingly irregular. 



This last point is even more evident from the following, however. 

 The culture was left at 35 varying a little to either side till 8 P.M., 

 and another rodlet selected' and measured, as follows : 



A.nd on analysing the doubling periods we find a considerable 

 retardation, evidently due to the variations in growth at the high 

 temperatures. 



Doubling periods : 



67-5 135 p. -= 8.19 P.M. 9.13 P.M. = 54 minutes at 35 -4 34-2537-5 35 '5 C. 



Calculated back : 

 166 -583 -25 p = 8.35 P.M. 9.31 P.M. = 56 m. at 34 -2537 -535 -2537 '75 C. 



It should be noted that the drop became copiously diluted after an 

 hour or so, by absorbing water, and the longer doubling period 

 (36 minutes with a range of 1 C.) from 4.28 onwards is possibly 

 referable to this rather than the age of the rodlet ; though I think 

 the latter fact of importance, as we shall see. 



On examining these curves of November 5 all from one culture be 

 it remembered we find that when first put in the doubling took 

 35 minutes, at 32 35'5 a range of 3'5 ; whereas the part growing 

 at 33'25 34-5 (a range of To ) only took 27 minutes, whence may 



