144 ORIGIN OF THE YEASTS 



yeasts. Nevertheless since the essential characteristic of the genus 

 Endomyces is the presence of a typical mycelium from which the ascs 

 spring exclusively, it seems that E. javanensis ought to be regarded as 

 a yeast. 



The information with regard to these various fungi explains anew 

 the phylogeny of the yeasts. Indeed, it is possible to regard the 

 genus Eremascus as an ancestral form. From this may originate a 

 form, quite hypothetical, related to Endomyces fibuliger, but differ- 

 ing by the existence of an isogamic copulation characteristic of Ere- 

 mascus. This copulation which is reduced to an 

 unfruitful attempt with E. fibuliger has completely 

 disappeared in E. capsularis. From this hypothetical 

 form the yeasts may derive by regression and from 

 the mycelial form which yields its place to yeast-like 

 forms. 



Fi 60 Ascs of Summarizing, this hypothetical fungus, derived 

 Endomyces deci- from Eremascus, may be the beginning of two 

 (after de branches, one with E. fibuliger and the E. capsularis, 

 the other with Zygosaccharomyces and the Saccharo- 

 myces. The genus Saccharomyces represents a parthenogenetic form 

 derived from Zygosaccharomyces. 



Now it remains to determine the origin of the Schizosaccharo- 

 myces. The study of two other forms of the genus Endomyces, the 

 E. Magnusii and the E. dedpiens, has given some information on the 

 subject. 



These two fungi resemble very much, in the whole of their develop- 

 ment, E. fibuliger; but they are closely distinguished by the fact 

 that, in place of producing yeast-like bodies, they form, by dissocia- 

 tion of their mycelium, cells called oidia which are capable of dividing 

 transversely like the cells of Schizosaccharomyces. (Fig 59.) Let us 

 state that, in certain media, a true mycelium is not formed but 

 almost always oidia which multiply like the Saccharomyces. In its 

 general form, the oidium is identical to the cell of Schizosaccha- 

 romyces. Cytologically, however, it differs more often in E. Magnusii 

 by the presence of many nuclei. Nevertheless, many of the oidia 

 of E. Magnusii offer only a single nucleus and Dangeard has shown 

 that in the oidia of E. dedpiens, this is always the case. 



These two fungi present also chlamodyspores which are formed like 

 oidia by a sort of dissociation of cells in the mycelium but are dis- 

 tinguished by the formation of a very thick membrane and by the 

 fact they cease to divide until they find conditions sufficiently favor- 

 able. These, then, are sort of encysted oidia and may be compared 

 to the durable cells of yeasts. 



