ALCOHOLIC FERMENTS. 249 



and does not excite alcoholic fermentation ; neither does it 

 invert solutions of cane-sugar. 



The colonies on the surface of the gelatine are light grey, 

 dull, and spread out like a film or hollowed like a shell. By means 

 of this macroscopic appearance Mycoderma is readily dis- 

 tinguished from the ordinary Saccharomycetes, which, on the 

 same medium, form light greyish-yellow colonies with a dry 

 or lustrous surface, and a more or less arched form. Sacch. 

 membrancefacicns, which differs so markedly in its biological 

 behaviour, and which very rapidly gives a strong film on the 

 liquid, alone resembles Mycoderma in its behaviour on plate 

 cultures. 



The form of film described was obtained by HANSEN when 

 lager beer had been exposed in open vessels at temperatures 

 between 2 and 15 C. ; at 33 C. development still occurred, 

 but at temperatures above 15 C. this species gave place more 

 and more to competing forms. As low temperatures are 

 favourable to its development, it will readily thrive in the 

 storage cellar, especially as lager beer forms a much more 

 favourable medium for its growth than wort. This is seen to 

 be the case when traces of a pure film are introduced into 

 lager beer and wort, contained in open vessels, and then left 

 to develop ; the culture in lager beer nearly always remains 

 pure, while in wort various other species make their appearance. 



In HANSEN'S comprehensive series of experiments on Carls- 

 berg beer, it was always found that both lager and export 

 beers were attacked by this fungus ; but there was never the 

 slightest indication that the beer had acquired any disease 

 from this source. The fungus was widely distributed just at 

 those periods when the beer was found to be particularly 

 stable and of good flavour. This has also been confirmed by 

 numerous experiments on lager and export beers conducted by 

 GROENLUND and A. PETERSEN, and those carried out in the 

 author's laboratory. It is self-evident that we are only speak- 

 ing of beer which has been properly treated. In imperfectly 

 closed bottles and casks, Mycoderma ceremsice will of course 

 rapidly develop a film, which is sufficient, unaided, to destroy 

 the product. 



BELOHOUBEK was the first to find that, under certain con- 



