We procured from Arbois, on January 20th, 1875, some wine yeast taken from a large barrel of the preceding vintage, racked on January 18th. The ferment was very irregular. Some of its cells were very old, of a yellowish colour, and full of granulations—amongst these a certain number formed jointed segments, rather elongated, and probably belonging to _saccharomyces pastorianus_. The other cells were transparent, and apparently still young. This mixture of the two ferments is represented in Fig. 57. No doubt if we had searched carefully we should also have found some cells of _saccharomyces apiculatus_. On January 21st we sowed a small quantity of this raw yeast in a flask of sweetened water. On the 24th we poured off the liquid, and supplied the deposit with fresh sweetened water. The exterior temperature was 12° C. (54° F.). On the 27th we took some of the deposit and put it into a flask of wort. The following days there was a development of yeast, accompanied by fermentation. We obtained, however, neither the large forms of the ferments of fruits, nor those of the more minute ferments represented in Plate XI. The _saccharomyces pastorianus_, represented in the yeast which we sowed by aged, granular, elongated cells, had, therefore, not revived. Fearing that this result might have been attributable to insufficiency of the exhaustion, which had only lasted for a few days, we raised the temperature of the flask of sweetened water to 25° C. (77° F.), at which we kept it until February 20th. On that day we sowed some of this yeast in wort. There was a very perceptible revival the next day, but it was still impossible to detect with the microscope the forms we have just mentioned, nor did _saccharomyces pastorianus_ appear in fresh, succeeding growths. [Illustration: Fig. 58.] Fig. 58 represents the yeast formed, which evidently had sprung from the transparent cells seen in Fig. 57, and doubtless belonging to the ordinary ferment of wine, _saccharomyces ellipsoïdeus_. Here we have another example of the natural separation of ferments brought about by the death of one or two of them, or by extreme differences in the time of their revival. We cultivated this yeast (Fig. 58), to some considerable extent, in beer-wort. It produced a peculiar beer, of vinous character, in fact a true _barley wine_. This proves, we may here remark, that ordinary wine, in its flavour and quality, depends to a great extent on the specific nature of the ferments which develop during the fermentation of the vintage; and we may fairly assume that if we were to subject the same must to the action of different ferments we should obtain wines of different characters. With a view to the practical application of this idea, it would be well to undertake new studies in this direction; and the methods of cultivating and managing ferments, explained in this work, would be of great value in such researches.