Report on the Bacteriology of Water. 419 



A somewhat remarkable fact was observed in these July 28 

 cultures. After standing all night at 32- 75, falling to 26 at 10 A.M. 

 on the 29th July, both the cultures had passed over into spores. 



That is to say, at temperatures between 23'5, rapidly rising to 26, 

 then up to 33 C., slowly falling to 26 again, two cultures passed 

 through their cycle from spore to spore in twenty-seven hours. 



It would be interesting to investigate the properties of these 

 spores thus rapidly formed at high temperatures, a,nd compare them 

 with others. 



It is noteworthy that the culture of July 27, though treated exactly 

 similarly from 8 A.M. 28th, to 10 A.M. 29th July, had as yet formed, 

 no spores. This latter had grown far more luxuriantly, however 

 (at 27'5 on the 27th, see record), and served to show that the higher 

 temperatures of the 28th culture, though driving the organism to 

 more rapid spore formation, inhibit the growth, as the curve shows. 

 It should also be noted that the spores formed were small, and, 

 in many filaments, sparse, though otherwise normal to all appear- 

 ance. 



On July 29, spores, in broth -f 1 per cent, gelatine were started 

 at 10.15 A.M., the temperatures running as follows : 



Temp. 



I now sought for a filament, and was surprised to find what rapid 

 progress had been made, for two were found of 67"5 and 70 p, respec- 

 tively. The shorter was chosen for measurements. 



Doubling period : 



1. 67 -5125 p = 2.30 P.M. 3.7 P.M. = 37 minutes at 25 -626 -2 C 



2. 125 250 = 3.7 -3.44 =37 26 -2 25 "75 C. 



