ALCOHOLIC FERMENTS. 187 



species, these species being again distinguished by a series of 

 special characters. The following systematic descriptions are 

 chiefly based upon the results of HANSEN'S experimental 

 researches. According to this investigator, it is considered 

 probable, for many reasons, that the oval form of yeast-cell is 

 the original one, and that the different, more or less marked 



o 



Pastorianus growths have developed from it. 



SACCHAROMYCES CEREVISLE I. (HANSEN). 1 (Figs. 47-49.) 



This and the five following species (Sacch. Pastorianus I., 

 IL, and ///., Sacch. ellipsoideus L and //.), all develop inver- 

 tase and maltase ; with these they effect the hydrolysis of 



FIG. 47. Saccharomyces cerevisise I. (HANSEN). Cell-forms of young sedimentary 

 yeast (after HANSEN). 



saccharose and maltose to invert sugar, and ferment the latter. 

 They produce a vigorous fermentation in dextrose solutions, 

 and likewise in maltose solutions, especially when a nutrient 

 liquid such as yeast- water is added. All are vigorous alcoholic 

 ferments, which in the course of fourteen days, at the ordinary 

 room-temperature, readily produce 4 to 6 per cent, (by volume) 

 of alcohol in beer-wort. They are unable to ferment lactose. 



Saccharomyces cerevisice I. is an old English top-fermentation 

 yeast, which is employed in breweries in London and Edinburgh. 



The young growth of sedimentary yeast (Fig. 47) developed 

 in wort, consists essentially of large round and oval cells; 

 really elongated cells do not occur under these conditions. 



1 This top-fermentation yeast must not be confused with HANSEN'S Carlsberg 

 bottom-yeast No. 1 



