ALCOHOLIC FERMENTS. 165 



hairy at the edges. A microscopical examination shows that in 

 this case the two species are also distinguishable morphologically. 

 This is not by any means always the case with cultures in 

 solid media ; in fact, the differences are often less marked under 

 such conditions than when nutritive liquids are employed. 



For the Mycoderma species and Sacch. membrancefaciens, 

 HANSEN has discovered a characteristic behaviour in wort- 

 gelatine, in which they form shield-like colonies readily 

 distinguishable from those of the Saccharomycetes. 



In this connection we may mention HANSEN'S observation 

 that some species, e.g., Sacch. Marxianus and Sacch. Ludwigii, 

 can develop a mycelium when grown in a solid medium, while 

 others are unable to do so. 



In the case of certain cultivated yeasts, P. LINDNER has 

 noted distinct differences in their growths on gelatine. 



WILL and others have shown that the characteristics 

 exhibited by cultures on nutritive gelatine are often very 

 variable. 



ADERHOLD, during an examination of gelatine-growths of 

 German ellipsoid wine yeasts, found that in puncture-cultures 

 and in drop-cultures two types were distinguishable, one of 

 which showed colonies with funnel-shaped depressions and 

 with marked concentric lines, whilst the other showed conical 

 growths with indistinct concentric structure, but very promi- 

 nent radial streaks. 



A great number of yeast species render nutrient gelatine 

 liquid. This was proved by the author in 1890 with regard 

 to brewers' high-fermentation yeasts. More recently, similar 

 observations have been made with regard to various other 

 yeast species by WILL, WEHMER, FISCHER, and others. 



(/) The Behaviour of the Saccharomycetes and Similar 

 Fungi towards the Carbohydrates and other Constituents 

 of the Nutritive Liquids. Diseases in Beer. The first 

 striking proof of the fact that Saccharomyces species may 

 produce very different reactions in the nutritive liquid, was 

 obtained by means of pure cultures of the yeasts prepared in 

 the Carlsberg laboratory, afterwards in the author's, and later 

 on in many other laboratories, and which were subsequently 

 introduced in practice. There are breweries in which a con- 



