ALCOHOLIC FERMENTS. 157 



It is a widely-known phenomenon, that fermented liquids 

 become coated with films. The films formed by the budding- 

 fungi Mycoderma cerevisiaz, Mycoderma vini have especially 

 attracted attention. The frequent mention of such films in 

 the literature of our subject led to a result well known in 

 other branches of science ; they had been referred to for so 

 long as though well understood that at last the belief in 

 the actual existence of this knowledge became firmly rooted. 

 After HANSEN had submitted this question to an experimental 

 investigation, he showed, however, that this view was 

 erroneous. 



HANSEN has dealt with a large number of films, and amongst 

 them are several forms most closely related to different species 

 of Saccharomyces Mycoderma, which do not produce endogenous 

 spores. According to DE SEYNES, EEESS, and CIENKOWSKI, 

 these Mycoderma-species do yield ascospores ; it is, however, 

 highly probable that these investigators were dealing with 

 impure films containing an admixture of true Saccharomycetes. 

 It is, indeed, a matter of no little difficulty to determine the 

 purity of such a culture if one does not start from a single cell ; 

 for if Mycoderma cerevisice is cultivated as sedimentary yeast, 

 the cells assume an entirely different appearance from that of 

 the film-cells ; they are filled to a great extent with plasma, 

 whilst the cells of the film are, as is known, poor in plasma 

 and contain strongly-developed vacuoles. Such forms, which 

 are generally regarded as Mycoderma cerevisice, readily and 

 quickly form films ; some simultaneously exhibit distinct signs 

 of fermentation, whilst others do not. On beer and wort 

 these films are grey and dry in appearance ; afterwards they 

 become wrinkled and lighter in colour ; air is found freely 

 intermixed between the cells. Some of the varieties of Torula 

 investigated by HANSEN yield similar films ; the film of 

 Chalara Mycoderma, on the other hand, is glutinous, tough, and 

 slightly lustrous. In the case of Monilia which, as pre- 

 viously mentioned, may occur with budding cells the film- 

 formation is peculiar: even during vigorous fermentation a film 

 forms on the bubbles of foam, spreads gradually over the 

 whole surface, and sometimes becomes wrinkled. Thus, the 

 cells in the flask first sink to the bottom as sedimentary yeast, 



