VARIATIONS IN THE SACCHAROMYCETES. 283 



wort, is apt to lose this power for a time if preserved in an 

 aqueous solution of cane sugar. 



A similar proof of a variation in brewers' low-fermenta- 

 tion yeast, due to the composition of the nutrient liquid, 

 was furnished by Seyffert, who found in the case of a selected 

 type which, after long use in breweries, had lost its good 

 properties with regard to clarification, that it was possible 

 to restore it to its original condition by treatment with lime. 

 Gypsum was added either to the wort, the brewery water, or 

 the steeping vat, and from wort prepared in this way wort- 

 gelatine was concocted, in which the degenerated yeast growth 

 was sown for fresh pure - cultivation. On development of 

 the colonies in small flasks, these new growths showed true 

 " breaking " and the power of adhering to the bottom of the 

 flask ; the qualities thus regained were retained during the 

 use of this yeast in practice. 



Another example of physiological transformation is the 

 following : The three species described by Hansen under the 

 name Saccharomyces Pastorianus form a dough-like sediment 

 under certain conditions similar to those of the other Saccharo- 

 mycetes ; under other conditions, however, a film-like, wrinkled, 

 or caseous sediment consisting of small lumps (Pasteur's 

 levure caseeuse) a sediment of very different appearance. 

 In the latter case, the fermenting wort also assumes a charac- 

 teristic appearance, and, contrary to what ordinarily occurs, 

 remains bright throughout the fermentation, so that yeast 

 flakes may be observed rising to the surface and sinking 

 again to the bottom. If this curious sedimentary yeast is 

 repeatedly cultivated by new fermentations in wort, it can 

 be again transformed into the dough-like condition. 



Both Hansen and the author established the fact that by 

 long storage under ice, and subsequent growth in wort, a 

 brewery bottom-fermentation yeast exhibited top-fermenta- 

 tion phenomena, which, however, by continued pitching 

 gradually but entirely disappeared. Similar observations have 

 been made by Will. 



We also find a transitory physiological transformation in 

 film-formations of the Saccharomycetes. 



4. In 1889, Hansen published the results of a series of 



