_1st bottle._—On May 7th we observed little particles of fungoid growth on the surface of the liquid, and at the bottom were large flakes of _mycelium_. On May 11th a veil of _mycoderma vini_ had formed: there were no signs of fermentation. On May 13th vigorous fermentation commenced; it lasted until May 23rd. The microscope revealed yeast in globules of two sizes, the larger of which were considerably less numerous than the others. There were no signs of lactic or butyric ferment. _2nd bottle._—May 7th, particles of fungoid growth on the surface of the liquid, and also a veil of _mycoderma vini_. On May 11th, 13th, and up to the 23rd, no signs of fermentation were visible. On May 30th fermentation was active. The microscope showed us yeast mixed with butyric _vibrios_. In this case, alcoholic ferments had come into existence, and from the precautions taken at the moment when the liquid was brought into contact with the external air, it is certain that the advent of the germs of those ferments, as also those of the other organisms which made their appearance—the fungoid growths, _mycoderma vini_ and _vibrios_—could only be accounted for by the fall of particles of dust floating about in the room. It follows, then, that under certain circumstances germs of alcoholic ferment may be found floating in the air; but we can readily show that the peculiar conditions of the place had a large share in bringing about the results obtained by the foregoing experiment. The same day, May 2nd, 1873, we uncorked, with the precautions that we have already described, four other bottles of the same must. These were placed in a room which was used less frequently than the preceding one, and in which experiments relating to fermentation were seldom conducted. _1st bottle._—On May 8th we observed on the surface of the liquid large, frothy pieces of mycelium (_mucor mucedo_ or _mucor racemosus_). The liquid was perfectly bright.[40] May 30th.—No signs of actual fermentation yet visible. _2nd bottle._—On May 8th we noticed a thin, greasy-looking scum on our liquid, which had become turbid and acquired a sour smell. The microscope showed that this scum was formed of _mycoderma aceti_. On May 30th the scum had assumed a whitish appearance, and seemed to be dead; there was a green spot of _penicillium glaucum_ upon it. No signs of fermentation. _3rd bottle._—May 8th, patches of fungoid growth on the surface of the liquid. May 30th, thick and abundant fungoid growth, but no fermentation. _4th bottle._—May 8th, little patches of fungoid growth, and a scum of _mycoderma vini_. May 30th, still no fermentation. Up to the month of August, 1873, not one of these bottles gave the least sign of alcoholic or other fermentation.