The following is one of the most curious of the forms presented by _saccharomyces pastorianus_, occurring after exhaustion in a sweet mineral liquid. The ferment, taken from a closed vat, in which it had been used for beer, was sown in the mineral liquid on July 4th, 1873. The following days the ferment developed feebly, but perceptibly, and gradually increased in bulk. The flask was left to itself in an oven at 25° C. (77° F.) until December 3rd, when we ascertained that all the sugar had fermented. We then sowed a trace of the deposit, which had become abundant, in a flask of pure wort. On December 4th there was no perceptible change. On December 5th, however, fermentation was in active progress; a large quantity of froth covered the surface of the liquid, and a considerable deposit of ferment had already taken place at the bottom. We made a microscopical examination of this deposit, a sketch of which we append (Fig. 37). The dark, double-bordered cells are those which were sown but did not rejuvenesce. We may notice in different places several of these same cells, recognizable by their granular contents, which they are beginning to lose, to make room for germinating cells and joints, often numerous. For instance, in the group at the bottom of our figure one of the cells is in course of rejuvenescence and germination, and has given rise to no fewer than six cells, filaments, or groups of filaments. In different fields of our microscope we met with a crowd of branches, more or less ramified, and chains of cells, of greater or less length, of which we have sketched a few. In proportion as the budding of these branches is repeated, the cells and joints become more readily disunited, grow small, and assume the appearance of _saccharomyces pastorianus_ in ordinary growths, almost as represented in Plate XI. At first, when the old, exhausted cells begin to germinate, their appearance rather resembles that of _dematium pullulans_, as seen in the germination of many of the corpuscles on the surface of clusters of grapes or fruits, or their woody parts, some specimens of which are to be found in Plate IX.