For a long time, like Turpin and many other observers, although we had no belief in the transformation of _mycoderma vini_ into any one of the common moulds, yet we did believe in its transformation into alcoholic ferment. In the course of more elaborate researches, however, we at last discovered that our previous experiments had been vitiated from the same source of error which we have so often had occasion to point out as affecting the observations of our opponents, namely, the fortuitous and spontaneous introduction, unknown to the experimentalist, of germs of the very plant for whose appearance by way of transformation he is seeking. When we consider that every fermented vinous liquor, when put on draught, is liable to efflorescence, it is difficult to avoid the supposition that this efflorescence is primarily due to cells of the yeast that has caused the liquid to ferment, from which cells the liquid could not be completely freed, no matter how bright it might have been, and which come to the surface of the liquid to live after the manner of fungoid growths. We wished to test this supposition by means of experiments. So great, however, was the resemblance between the forms possible to yeast and mycoderma, of which latter efflorescence is really composed, that we quite despaired of being able to solve the question by microscopical examination, that is, by observing the actual conversion of a cell of yeast into a cell of mycoderma. In order, then, to overcome that difficulty, we endeavoured to produce an inverse transformation—that of mycoderma into yeast. We imagined that we should doubtless obtain this result by submerging some of the efflorescence of wine or beer in a saccharine liquid well adapted to alcoholic fermentation. By submerging the mycoderma we would do away with the ordinary conditions of life in this kind of fungoid growth; for we would thus prevent the supply of oxygen from the air, since that oxygen would always be excluded, in the most effectual manner possible, by the portion of mycoderma that would remain on the surface of the liquid, even after the submersion process; and on the other hand, we would be subjecting our growth to the ordinary conditions of ferment life, which acts at the bottom or in the bulk of liquids fermenting.