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Messrs. A. Downes and T. P. Blunt on [Dec. 19 ? 



them in darkness — the two tubes of Pasteur solution each contained 

 several tiny specks of mycelium. 



One of the two was on this again exposed to sunlight, and in it the 

 mycelial development was at once stopped ; the other tube was left in 

 the dark and the fungus gradually grew till it filled the whole space 

 of the liquid, which on microscopical examination was found to con- 

 tain no other organisms. The tube of urine remained clear till July 

 15th, 1878, — nearly ten months after incasement, — on which date 

 two specks of mycelium appeared, and subsequently developed as in 

 the previous case. No Bacteria could be seen on examination with an 

 immersion y y. It is noteworthy that a companion tube to this which 

 was incased after six days of insolation had developed a growth of 

 mycelium in three or four days. 



It would seem that in the three tubes above mentioned Bacteria, 

 or their " germs," had been either wholly destroyed or reduced to so 

 low a state of vitality that they were unable to develope in the fluids 

 in question ; while it is evident that the spores of the mould which at 

 length appeared, unless they had been accidentally shaken down from 

 the cotton- wool plugging the tubes, had undergone some change which 

 reduced them to a condition of torpidity from which in process of 

 time they emerged. Such a condition, we may perhaps conceive, 

 might be brought about by any influence causing thickening of the 

 cell- wall of the spore. We hope at a future time to offer some further 

 evidence on this question of revival of dormant germs, which is, we 

 think, of much interest. 



Prom a very early period of our inquiry we have set ourselves to 

 the task of investigating the intimate nature of the remarkable action 

 of light upon these organisms, and we have arrived, as we believe, at 

 a satisfactory solution of the problem, but in the first place it will be 

 well to describe some preliminary experiments. 



An interesting point to be determined was the question, — with what 

 part of the spectrum is this property of light associated. 



The observations made by us last year indicated that the rays of 

 greatest refrangibility were the most active, but the experiments then 

 made did not warrant any definite conclusions as to the part played 

 by rays of lower refrangibility. 



The method employed in the more recent experiments was similar 

 to that described in our former paper : — 



Small test-tubes containing the cultivation-fluid were suspended in 

 deep narrow boxes made of garnet-red, yellow, blue, and ordinary glass 

 respectively. Each box held about six test-tubes, and corresponding 

 series were incased in laminated lead. 



A spectroscopic examination of the glass of which these boxes were 

 constructed showed that the yellow and blue were far from being 

 monochromatic. The red was an excellent glass for the purpose. 



