ioo RESEARCHES ON YEASTS. 



length of time in aerated wort, and at a temperature approach- 

 ing its maximum temperature, it completely lost its power of 

 forming spores ; and even after numerous generations of vegeta- 

 tive cells had been produced in new wort cultures at favourable 

 temperatures, none were yet able to develop spores. In this 

 case, therefore, a property which is a very important one as 

 regards morphology and classification has been entirely de- 

 stroyed. Simultaneously with the loss of this faculty, the 

 power of film-formation in old wort cultures also disappeared. 



The treatment which the cells must undergo in order to 

 bring about such a deep-seated transformation, produces, in 

 fact, a revolution in their vital functions. That a long con- 

 tinuation of this treatment is necessary, is easy to understand 

 when we recollect with what tenacity the cells of the Saccharo- 

 mycetes retain their power of producing spores, even under 

 the conditions obtaining in breweries and distilleries where 

 they can only reproduce themselves through numberless 

 generations by the process of budding. 



I afterwards obtained similar results with various other 

 species ('Annales de Micrographie/ Fevrier 1890; 'Zeitsch. f. 

 d. ges. Brauw.' 1890, p. 145), and found that in beer wort one 

 group of them gives a quicker and more abundant growth, but 

 a slower fermentation than that produced by their progenitors. 

 Amongst these were also some brewery yeasts e. g. the Carls- 

 berg yeast No. 2. After this species had by the treatment 

 mentioned above been brought to the condition in which it 

 had completely lost the property of spore-formation and film- 

 formation, I made some comparative experiments with this 

 variety, and with the original yeast from which it had sprung, 

 under the conditions obtaining in the brewery. It was found 

 that during the primary fermentation, the newly-formed 

 variety attenuated more slowly and more feebly than the 

 orginal yeast, but at the same time the brightening was 

 better. After normal storage the difference in the attenuation 

 gradually diminished, and almost disappeared. The beer 

 produced by the variety, as a rule, brightened somewhat 



