Report on the Bacteriology of Water. 201 



The total growth in length from 8.10 P.M., when the length recorded 

 was 6 ft, to 10.35 next morning, when the length was 81 /<, therefore, 

 amounted to 75 /t in fourteen hours twenty-five minutes. This gives 

 an average growth of about 0'086 /i per minute, but the rate varied 

 considerably from time to time. Thus during the first thirty minutes 

 (from 8.10 to 8.40 P.M.) it was about 0*33 ft per minute. During the 

 next sixty-five minutes it averaged only about half that, amount, a 

 fact which puzzled me exceedingly, and which I thought might 

 possibly be explained by the germinal rod being engaged in prepara- 

 tion for its first segmentation ; for the first septum was visible shortly 

 afterwards. But during the next period, of ninety-five minutes, the 

 rate was apparently only about 0*12 ft per minute ; and during the 

 next forty-five minutes, almost the same average rate was observed, 

 whence I came to think the explanation temporarily entertained may 

 have to be abandoned. Then came the break in the observations. 

 During the night 11.45 P.M. to 10.35 A.M. = 650 minutes the 

 total growth was 45 /t, i.e., about 0*66 /t per minute on the average. 



From the general slowness of growth of this specimen, I was more 

 inclined to suppose that the medium (3 per cent, glucose solution) 

 was less adapted for the needs of the organism than broth is, a con- 

 clusion fully borne out by tube-cultures, and subsequent experience. 



Spores sown in ' broth at 15 C. at 3 P.M., had given rise to 

 vigorously growing plants next morning, the long filaments of 

 which were already breaking up as described on p. 279. One of these 

 partial filaments was fixed under the micrometer scale, each division 

 of which corresponded to 3 /*, with the combination (E/4) used. The 

 filament was quite straight, and its ends were covered by the llth and 

 38th divisions respectively when the observations began. During the 

 whole period the temperature was 15 to 16 C. and did not fall or 

 rise outside those limits. Moreover, I kept the microscope at a north 

 window, and by means of cardboard screens and by turning the 

 mirror between the observations, prevented any access of direct light 

 such as might possibly be suspected of inhibiting the growth. 



At 10.18 the filament was straight and measured 27 divisions of 

 the scale in length i.e., it was 81 /t long, and the following shows the 

 growths at successive intervals. 



