216 STUDIES ON FERMENTATION. 



rather rapidly, in thick, greasy-looking pellicles, on the surface 

 of liquids which have been fermented by means of caseous 

 ferment. The larger form of cells, a and h, is not often met 

 with. 



On May 27th, 1875, we sowed, in a flask of wort, a trace 

 of a pellicle of this kind, which had formed on the surface 

 of a flask in which fermentation had been set up by means 

 of caseous yeast in May of the preceding year. On May 

 30th fermentation began to reveal its presence by a voluminous 

 froth, and the newly-formed yeast had reached the bottom 

 of the flask. A small quantity was taken out by a capillary 

 glass tube, and a sketch of the ferment made ; this is given 

 in Fig. 54. Amongst the cells which occupy the field there 

 are groups of some of larger size. These are not distinct forms 

 mixed with the others, but simply another illustration of the 

 fact that old cells in course of revival, especially when they 



Fig. 54. 



have been exhausted in sweetened water, as we have just 

 observed of the aerobian ferment of " low " yeast, commence 

 with forms of larger diameter or more elongated than the 

 ordinary forms peculiar to the ferment which at a later stage 

 are developed from them. We have seen how marked and 

 exaggerated this feature was in the case of saccharomyces 

 pastorianus. 



Let us again call attention to the forms of aerobian ferment 

 furnished by the yeast which we have already described under 

 the name of new ''liigh" ycad. Fig. 55 represents this 



