Report on the Bacteriology of Water. 341 



On leaving the cultures through the night, at about 12 13 C., 

 and examining at 9 A.M. next day, the one over bichromate had 

 filaments from 220 /* to 660 /t long, whereas none in the blue light 

 were more than 88 ft, to 130 ft long. 



Since the variations in temperature (N.B. The rapid and extreme 

 variations only refer to the control cells, and were made for experi- 

 mental purposes) only concern the exposure of the, as yet, tin- 

 germinated spores, we can hardly err in referring the retardation of 

 the spores in the blue-light to the inhibitory action of the light rays. 



At 7 A.M. I sowed spores in gelatine- broth, and exposed forthwith 

 at an east window. The cells had a quartz floor, and a plate of glass 

 covered with tin-foil was put over them to keep the sun off the top 

 glass. One was over red glass, the other over blue, and neither 

 received any but rays reflected through these glasses from the micro- 

 scope mirrors. 



Each had a dummy cell by its side, arranged similarly, the tem- 

 peratures of which ran as follows : 



Blue. Eed. 



Time. C. C. 



7.0 A.M. 17-5 17-5 



9.15 20 20 



9.45 22-5 22-5 



10.20 24 24 



12 noon 23'5 22 



3.45 P.M. 20-5 20-5 



The day was bright, and every care was taken to keep the direct 

 sun's rays off by means of shutters, &c. 



At 4 P.M. both cultures were removed to the south window, where 

 the temperature was 21 C., and kept so till near 7 P.M., at which 

 hour it had fallen to 20 C. It slowly fell during the night, as 

 shown by curve, to 19 21. 



The table on the next page gives the results (see also Curves 34 

 and 35, p. 343) : 



Here, again, the results seem definitely positive, and only to be 

 accounted for as due to the light rays, and one must conclude that 

 with resting spores at any rate the above exposure to reflected light 

 through blue glass causes very pronounced retardation, suggesting 

 that a little longer exposure (or a somewhat more intense light) 

 would have inhibited the germination entirely. 



