Report on the Bacteriology of Water. 



293 



at 4 o'clock there were certainly 23, and I believe more, per- 

 haps 25 or 2(5, but those most recently formed are very difficult to 

 see with the powers employed for measurements. 



The whole period of growth under observation was (from 10.18 A.M. 

 to 4 P.M.) six hours all but eighteen minutes, i.e., 342 minutes, and 

 during that period the total elongation (from 81 ft to 135 fi) amounted 

 to 54 fi, and taking the average length of the growing segments at 

 5 /i, this would agree very well with the above, and, so far as it goes, 

 is evidence in favour of the view I have supposed probable. 



Having regard to the paucity of exact measurements after 12.56 in 

 the above series, it is scarcely of value to note that the average rate 

 of increment over the whole period, at 15 C., seems to be about 0'15 /t 

 per minute ; and the less useful since we have seen that there are such 

 marked periods of slower and more rapid growth. Nevertheless, this 

 would amount to a good deal in, say, sixty hours ; if the germinal 

 filament from a spore 2 fi long continued to grow only at that 

 rate, the filament produced would be 600 fi long, and would be seg- 

 mented into from 100 to 200 bacillar segments. But this is far less 

 than actually occurs, as we shall see later. 



In the following case the spore was sown, in dilute broth, a little 

 after 10A.M., and was put under observation by 11 A.M. The tempera- 

 ture was then 16 C. ; but it fell to 15 by 4 P.M., and slowly down to 

 12 C. by 7 P.M. The spore was germinating at 12.10 P.M., when it 

 measured 3 /*. 



This gives a total growth of 19'5 /i in six hours and fifty-five 

 minutes, with an average growth of 0'09 /* per minute if the rate 

 were constant. 



I was unable to distinguish any trace of a second septum up to 

 6.45, but at 7.5 the rod showed a perfectly sharp median septum, and 

 two extremely faint secondary septa one on each side. 



1 thought there could be little doubt that the sharp fall in the rate 

 of growth at 6.27 and 6.45 was associated with the process of cell- 



