VARIATIONS IN THE SACCHAROMYCETES. 285- 



showed no film-formation, contained 5-5 per cent, of alcohol 

 a quantity equal to that found at the end of the first 

 month. 



In another series of experiments Hansen showed that the 

 action of higher temperatures upon the cells without aeration 

 was capable of producing radical and lasting alterations of a 

 different kind in the nature of the protoplasm. When Carls- 

 berg yeast No. 1 was cultivated in wort at 32 C. through 

 eight cultures, each successive culture being inoculated from 

 the preceding one, which had been left undisturbed until the 

 end of the fermentation, a variety was evolved in the ninth 

 culture which produced 1 to 2 per cent, by volume less alcohol 

 than the original form, in wort of 14 Balling, containing 10 per 

 cent, of saccharose. The new variety clarified better under 

 brewery conditions, and gave a weaker attenuation at the 

 end of the primary fermentation ; a similar behaviour was 

 noted in the case of other species. 



(6) Hansen also succeeded, by cultivation in nutrient 

 gelatine, in producing new stable varieties. 



Thus, two varieties of Carlsberg low-fermentation yeast 

 No. 1, each generation of which was transferred to the surface 

 of wort-gelatine, attained a fermentative power superior to that 

 of the original forms. The difference is still more marked 

 when cultures are developed from spores of the top-fermenta- 

 tion yeast S. cerevisice I. on yeast-water gelatine. The new 

 varieties produced 3 per cent, more alcohol than the parent 

 form. 



The observations already detailed regarding asporogenesis 

 lead to the interesting conclusion that a species can lose one of 

 its characteristic properties as a result of external influence, 

 and that virtually a new species is produced. 



In the course of Hansen's experiments on spore transfor- 

 mations brought about by the action of temperature and 

 aeration, it was observed that if cells of successive generations 

 were removed many were affected even in the first growths 

 under the new conditions ; this modification, however, is tem- 

 porary in character ; it is only after successive generations 

 have been allowed to develop through continued inoculation 

 under the new conditions that the acquired characters become 



