330 MICRO-ORGANISMS AND FERMENTATION. 



carried out at room temperature in sterilised, hopped wort 

 contained in tall cylindrical glasses covered with several 

 layers of filter paper. After the primary fermentation was 

 completed, the liquids were poured into sterile flasks and 

 allowed to stand at low temperatures. The amount of alcohol 

 was determined at the completion of the primary fermentation 

 and again after the first fortnight of the secondary fermentation, 

 and, lastly, after the following fortnight. The primary fer- 

 mentation was interrupted when the appearance of the cells 

 showed that the first vigorous development had ceased. In 

 this comparison no attempt was made to decide what quantity 

 of alcohol could be produced by the species during primary 

 and secondary fermentation. The object was simply to in- 

 stitute a comparison. 



The flavour of the fermented liquor was recorded after the 

 beer had undergone a secondary fermentation at a low tem- 

 perature in flasks closed at first with cotton-wool and after- 

 wards with ground-glass stoppers. 



1. (Fig. 64, a, and Fig. 65, a.) 



The cells during fermentation are comparatively small, 

 oval, and linked in chains ; among them occur big, round and 

 grotesque forms. 



The yeast lies rather loose in the flask ; if shaken it does 

 not distribute itself equally in the wort, but separates into 

 clots. 



Film - formation : After a lapse of 31 to 32 days a very 

 thin film covers almost the whole surface of the liquid. 



The cells of the film are of about the same size as those 

 seen during the primary fermentation ; some cells much 

 elongated. 



The spores, if developed at a low temperature, are small, 

 full of vacuoles, and slightly granulated ; as a rule, only one 

 or two in each cell. 



At 11 to 12 C. a few spores make their appearance on 

 the seventh day ; at 25 C. abundant development of spores 

 in forty hours. 



