192 CLASSIFICATION OF THE YEASTS 



between the Schizosaccharomyces and the ordinary yeasts. This genus 

 is characterized by a tendency to produce mycelial formations rather 

 well developed and the replacement of ancestral sexuality by a com- 

 pensating phenomenon or parthenogamy consisting in the fusion of 

 ascospores two by two. 



After this genus may fall the genus Saccharomycopsis (Schion- 

 ning) which only includes S. guttulatus and which is characterized 

 by ascospores in a double membrane resembling those of the Endo- 

 mycetes (Eremascus, End. fibuliger, and capsularis) . We shall separate 

 the Saccharomycopsis capsularis (Schionning) from this genus in order 

 to include it with the genus Endomyces. ' The investigations of Guil- 

 liermond with this species seem to indicate that it approaches E. 

 fibuliger when the mycelial formation and method of formation of the 

 ascs are considered. 



The genus Saccharomyces (Meyen) includes all yeasts in which the 

 formation of a mycelium is not observed and in which sexuality has 

 disappeared with the exception of a few species (yeast Johannisberg 

 II) in which the primitive copulation has been replaced by a fusion 

 between the ascospores (parthenogamy). 



Finally the genus Hansenia (Lindner-Klocker) characterized by 

 its special apiculate cells and hat-shaped ascospores terminates the 

 series. 



Since the Saccharomyces includes all brewery, distillery, cider 

 and wine yeasts and other industrial yeasts, and consequently a 

 large number, we shall, with Hansen, make six sub-groups according 

 to their fermentation reactions: First, Saccharomyces which ferment 

 saccharose, maltose and dextrose with no action on lactose. Sec- 

 ondly, Saccharomyces which ferment saccharose and dextrose but do 

 not ferment lactose or maltose. Thirdly, Saccharomyces which fer- 

 ment dextrose and maltose but not saccharose and lactose. Fourthly, 

 Saccharomyces which ferment dextrose but neither lactose, saccharose, 

 or maltose. Fifthly, Saccharomyces which ferment lactose. Sixthly, 

 Saccharomyces which produce no fermentation and in which the fer- 

 menting function is imperfectly known. 



In the fourth group, we shall include, with Hansen, two genera, 

 Pichia (Hansen), characterized by hemispherical ascospores, and 

 Willia, characterized by special-shaped ascospores having the form 

 of a derby hat. 



In the fifth group, we shall place the genus Monospora (Metsch- 

 nikoff), characterized by its ascs with a single ascospore, and the genus 

 Nematospora (Peglion), characterized by its asc with 8 fusiform asco- 

 spores with a long mycelium and the genus Coccidiascus (Leger), 

 which is characterized by a probable copulation preceding the forma- 



