
FINAL DECISIVE EXPERIMENTS 275 
In Plate XII., Fig. 36, a portion of a flake is 
shown that had been heated a few weeks before 
only to 100° C., which was crowded with Bacteria, 
together with only a comparatively small number of 
inorganic particles. The specks seen in the photo- 
graph are principally organic units; in other parts 
of the flake they were associated with Torule. 
In Fig. 37 a portion of a flake from an A solution 
which had been heated to 130° C. for ten minutes, © 
and subsequently exposed to light (during rather 
cold weather) for five weeks, is shown. All the 
flakes were absolutely crowded with large and small 
inorganic concretions, and no living organisms of 
any kind were found. 
In Fig. 38 a portion of a flake is seen from a tube 
that had been charged with some of the same solu- 
tion, and had subsequently been heated to 125° C. 
only, for ten minutes. The tube had been exposed 
to light side by side with the last, and also for a 
period of five weeks. The concretions in the flakes 
were extraordinarily large and numerous, and again 
no organisms could be found. Apart from the tem- 
perature to which this tube had been exposed 
having been rather lower, it differed from the last 
only in the fact that the tube was composed of uviol 
glass. The change in the flakes of silica is, there- 
fore, to be regarded as the combined effect of the 
high temperature, together with the subsequent 
action of light through this glass.1 
1 The researches of Prof. Quincke seem to indicate another possible 
cause of difference of a recondite character. Thus, in a recent paper 
in The Proceedings of the Royal Soctety (No. 521, A, p. 67) he says :— 
