1886.] Action of Sunlight on Micro-organisms, Sfc. 21 



with, white paper, having one side open, and tilted at such an angle as 

 to receive diffused light straight from the white clouds of the northern 

 sky. By no possibility could direct sunlight find an entrance. In 

 the box were placed maximum and minimum thermometers, each 

 pair with bulbs respectively incased or left bare. 



In September, 1883, using Cohn's solution five times the ordinary 

 strength, in five days, four out of six incased tubes were noted as 

 "turbid," and the other two as "hazy," with bacteria. The exposed 

 tubes were recorded "beautifully clear." At the end of two days 

 more the latter were still clear, but in each were specks of mycelium. 

 The survival of mycelial growth over bacterial has already been 

 alluded to in the present paper, and is seen in Dr. Jamieson's own 

 experiments. 



But mycelial growth itself may be hindered by diffused light. 



In March, 1884, a slightly acid Cohn's solution, two and a half times 

 ordinary strength, being specially selected, I found that at the end of 

 ten days •§- of the incased tubes contained mycelial specks, the six 

 exposed tubes being perfectly free. At the end of fifteen days my 

 notes were : — " Disks of mycelium plug -f of incased, -f of exposed ; 

 small tufts of mycelium in the remaining incased tube, and in one of 

 the exposed, three remaining exposed quite clear. The difference in 

 appearance of the two sets is remarkable." 



The means of the thermo metrical readings during two periods 

 were : — 



Encased. Exposed. 



g *■ i qqq /Max. 63-5° F. (17-5° C.) 64-0° F. (17-8° C). 

 feept. IBM.. { mm U . 7 F ( 7 . C) 45 . F ( 7 . 2 C) 



n /Max. 56'0 F. (13*3 C.) 57'8 F. (14-3 C). 



" " LMin. 35-6 F. ( 2-0 C.) 36"8 F. ( 2'6 C). 



As the incased tubes were the better absorbers, so are they now seen 

 to be the better radiators, and conditions of temperature were accord- 

 ingly slightly more adverse to development of organisms in them as 

 compared with the exposed. 



I now conclude this paper with a reference to the researches of 

 Herr Pringsheim on chlorophyll.* I refer to them with especial 

 gratification, as evidence of the truth of a generalisation which I had 

 ventured to draw from our experiments. 



The micro-organisms of our solutions may be regarded as examples 

 of protoplasm in its simplest forms, but there are no grounds for sup- 

 posing that this " life-stuff " should be subject to hyperoxidation by 

 light only when it exists in a Bacterium, or a mycelial thread. On the 

 contrary we have probably to deal with a general law, and, without 

 protective developments of cell wall, or of colouring matter which 



* « M. B. Akad. Wiss.," Berlin, 1879. 



