492 



Dr. A. Downes and Mr. T. P. Blunt on [Dec. 6, 



An important result, we venture to think, in connexion with series a 

 of Observation 8, is the appearance of mycelial fungus in the two tubes 

 which were longest insolated. 



In the course of our investigation we have found that, when Bacteria ap- 

 pear early and in large numbers in the solutions we have used, the mycelium 

 of Penicillium or other microscopic fungus is rarely seen, the Bacteria 

 apparently preoccupying the ground ; when, however, the development 

 of the Bacteria is from some cause retarded or prevented, we have fre- 

 quently found tufts of delicate mycelium submerged in our experimental 

 solutions, after they have been encased or removed into diffused light. 

 An example of this is seen in Observation 3, and other instances might 

 be cited. It is to be observed, however, that no mycelium appeared during 

 the period of exposure of a solution, except under the conditions here- 

 after stated, nor, indeed, afterwards, if this were sufficiently prolonged. 



"We infer accordingly that light may retard or altogether prevent the 

 appearance of mycelial fungi, but that its influence in this respect is 

 slower and less powerful than upon the Schizomycetes. 



May not this explain, in part at least, the sparing distribution of 

 Bacteria in ordinary air as compared with the prevalence of the spores of 

 Penicillium &c, a fact observed by Burdon (Sanderson and others, and 

 which our own experience tends to corroborate ? 



In the course of our investigation we found that, within certain limits, 

 the rapidity with which Bacteria appeared in the solution A was propor- 

 tionate to its dilution. This is illustrated in the following observation, in 

 which we took advantage of the greater resistance to decomposition of 

 the stronger solutions for the purpose of ascertaining whether diffused 

 light exerts any appreciable influence on the processes under considera- 

 tion. We had already observed that diffused light did not prevent the 

 appearance of Bacteria in a solution when made in the strength given in 

 the Appendix (A). 



Obs. 9. July 24. — Four solutions are prepared, so that — 

 I. is of the ordinary strength. 

 II. is twice as strong. 

 III. is 3 \ times as strong. 

 1Y. is 5 „ „ „ 



One tube of each solution respectively is placed — 



(1) In the dark ; 



(2) In the diffused light of a somewhat badly lighted room ; 



(3) In broad diffused daylight. 



The result is seen in the following Table : — 

 (1) In the dark : 



I. became turbid with Bacteria, July 27 



H. ,, 55 55 55 28 



HI- 55 55 5) 55 55 29 



IV. „ „ „ 5, Aug. 2 



