ALCOHOLIC FERMENTS. 179 



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

 tion yeast, brought about by the composition of the nutrient 

 liquid, was furnished by SEYFFERT, who found that it was 

 possible, in the case of a good selected type which, after long 

 use in breweries, had lost its good properties with regard 

 to clarification (breaking), to restore it to its original 

 condition by treatment with a lime salt. Gypsum was added 

 either to the wort, the brewery water, or the steeping-vat, 

 and from wort prepared in this way wort-gelatine was con- 

 cocted, 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, and 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 under the group 

 Saccharomyces Pastorianus form under certain conditions a 

 dough-like sediment similar to those of the other Saccharo- 

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

 or caseous sediment consisting of small lumps (PASTEUR'S levdre 

 caseeuse), that is to say, sediment of very different appearance, 

 and yet produced by the same species. In the latter case, the 

 fermenting wort also assumes a very characteristic appearance, 

 and, contrary to what ordinarily occurs, remains bright through- 

 out 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. 



Finally, we also find a transitory physiological transforma- 

 tion in the film-formations of the Saccharomycetes. 



4. At the beginning of the year 1889, HANSEN published 1 

 the results of a series of experiments which were undertaken 

 with the hope of discovering the conditions causing variation, 

 and of experimentally bringing about the formation of new races, 

 and if possible new species. He has recently published additional 

 work on the subject. 



1 Centralbl. f. Bakt. u. Parasitenk., Bd. V., p. 665, 1889. 



