10 THE AMERICAN MONTHLY [Jan., 



distinguished from those of the true yeasts.* At c we 

 find some rectangular cells more refractive than those of 

 a yeast, and with vacuoles ; d shows cells of a pastorian 

 form. 



The spore-culture showed. 



1. Spores in the round or oval cells by 25° after 40//. 

 Spores also in the pastorian cells. The first are spores 

 of a cultivated yeast, the latter not. 



2. By 15° C. : After 40/^. no spores, after 72/i. spores 

 in the pastorian cells, typical wild yeast spores. 



An absolutely pure culture showed that this wild yeast 

 was Sacch. pastorianus III Hansen. 



The spore-culture was overgrown with a mass of rec- 

 tangular cells of a low refractive power (grayish appear- 

 ance). These belong to Mycoderma cerevisice Desma- 

 zieres,f and this species is not difficult to determine. On 

 beer or wine exposed to the atmosphere, a gray, greasy 

 looking zoogloea generally appears after a few days- 

 The zoogloea soon becomes uneven at the surface. The 

 cells are not easily separated, but aggregate in small 

 lumps in the field of the microscope. 



LITERATURE. 



A. Joergensen : The micro-organisms of fermentation. 

 London, 1889. 



Papers by Hansen, Holm and Poulsen in Meddelelser 

 fra Carlsberg Laboratoriet, Vol. I — III (1878—1893) : pa- 

 pers on spore-formation. 



cells, so it does not belong to the true Saccharomyces. The cells are always 

 readily recognized on account of their typical shape. 



*0n the limitation of these, see Bay (Amer. Naturalist XXVI, p. (j94-(i9fi, 

 1892). • 



tMyc. cerev. and 31. vini cannot theoretically be separated from each other. 

 Many text books state that these forms have spores ; this was stated by .T. oe 

 Seyues in 1868 and was repeated by others (see HeBary : Comp. Morph. and 

 Biol., 1887. p. 268), though practical work shows that the ?fi/codenna does 

 not have spores, and that, owing to the uncertainty of the species-question in 

 1808. De Seynes must have been Avorkiug with true yeasts. 



