146 ORIGIN OF THE YEASTS 



lined. The budding yeasts are sprung from a hypothetical form, 

 Endomyces a, analogous to End. fibuliger but have kept the copula- 

 tion of Eremascus. This copulation persists in the Zygosaccharomyces, 

 no trace of it remains in the Schwanniomyces, disappears completely 

 in the Saccharomyces and is replaced by a parthenogamy between the 

 ascospores in the yeast Johannisberg II. The Schizosaccharomyces 

 spring from a hypothetical form, Endomyces b, related to End. Mag- 

 nussii but with isogamic copulation. The Schizosaccharomyces seem, 

 like other yeasts, to be more advanced toward parthenogenesis as is 

 evidenced by a variety, Sch. mellacei, which has lost its sexuality. 



. Eremascus fertilis 



Endomyces \3^^ ^ , 



^f ^yEndomyces a 



Endomyces MagnusjJ, 



Indomyces fibuliger 



Endomyces capsularis 

 Zygosaccharomyces 



Schwanniomyces 

 Saccharomyces 



Endomyces **aecipiens 



Schizosaccharomyces/ octosporus 

 Schizosaccharomyces/ Pombe 



Schizosaccharomyces 

 mellacei 



Parthenogenetic variety 



Yeast Johannisberg II 



\ 



Summarizing, it seems proper to consider the Saccharomyces and 

 other budding yeasts and the Schizosaccharomyces as derived from a 

 form related to Eremascus fertilis. From this common stock, two 

 branches spring: one which forms the E. Magnusii and Schizosaccha- 

 romyces, the other which forms E. fibuliger, the Zygosaccharomyces 

 and the budding yeasts. The question of the phylogeny of the yeasts 

 may be considered today as a little more settled. 1 



1 Another theory has been recently proposed by Nadson following his dis- 

 covery of Nadsonia fulvescens. According to this author the Endomycetaceae 

 and the Saccharomycetaceae represent degraded forms derived from the higher 

 Ascomycetes. The yeasts possess a copulation in the germination of the ascospores 

 with Saccharomyces Ludwigii being an archaic yeast. This theory lacks a solid 

 foundation because it does not provide for any of the links between the higher 

 ascomycetes and the yeasts. On the contrary, Guilliermond's theory rests on a 

 series of known facts. 



