CLASSIFICATION OF THE YEASTS 191 



Finally in the fifth group (Saccharomycetes doubted by Hansen) 

 we shall include the genera Monospora, Nematospora, and Coccidiascus, 

 which offer by the shapes of their ascospores very special charac- 

 teristics and of which the affinities are not well known. 



The first group includes only the genus Schizosaccharomyces repre- 

 sented by only a few species. 



In the second group we shall place the genus Zygosaccharomyces, 

 first characterized only by isogamic or heterogamic copulation which 

 precedes the formation of the ascs and which seems to make up with 

 the Schizosaccharomyces an archaic type which has retained an an- 

 cestral copulation similar to the Eremascus. Next comes the genus 

 Debaromyces (Klocker) characterized by its ascopores in thorny mem- 

 brane. This genus actually includes only a single species Deb. glo- 

 bosus which has a copulation similar to the Zygosaccharomyces and 

 appears to progress toward heterogamy. The new genus Nadsonia 

 (Guilliermondia) of Nadson and Kinokotine, created for species with 

 heterogamic copulation, is characterized by the fact that the asc is formed 

 from a cell and a bud from that same cell. The ascospores, generally 

 to the number of one, resemble the ascospores of Debaromyces. They 

 have a large fat globule in their center and a membrane slightly 

 verrucose. The genus Schwanniomyces (Klocker) includes only Sch. 

 ocddentalis which is characterized by a thorny membrane but belted 

 by a projecting collar. Here the ascs have preserved traces of sexual 

 attraction and attempt to anastomose two by two before sporulation. 

 The genus Torulaspora, created recently by Lindner for yeasts which 

 present the typical spherical shape of the Torula, is badly defined; 

 however, we shall reserve for it a place along with the Schwanniomyces 

 because the ascogenic cells show traces of sexual attraction. We 

 shall include in this genus, by the side of Torulaspora Delbriicki 

 (Lindner), a certain number of yeasts which offer equally a spherical 

 shape and which, on the other hand, have preserved traces of sexual 

 attraction (yeasts E and F of Rosa for instance) . 



The third group, one large in numbers, includes the genus Sac- 

 charomycodes (Hansen) in which the cells multiply by a process in- 

 termediary between transverse partition and budding, and which, 

 from this point of view, may be regarded as a form of transition 



yeasts. Secondly, the Saccharomyces are divided into two groups only; the first 

 includes yeasts which form a scum only at the end of fermentation. This scum 

 is mucous without occluded air bubbles. This group includes the genera Sac- 

 charomyces, Zygosaccharomyces, Saccharomycodes, Saccharomycopsis. The second 

 group includes the types which give a scum at the beginning with bubbles of air 

 in it: genera, Willia and Pichia. Thirdly, the genera Nematospora and Monospora 

 make up a group under the name of doubtful Saccharomycetes. 



