432 SACCHAROMYCES APICULATUS. 



confirmation of the previous discovery of certain chemists, e.g., 

 H. BUNGENER and L. WEIBEL (II.), that beer worts contain a 

 larger proportion of fermentable sugars, other than maltose, than 

 had been hitherto supposed, amounting probably to one-fourth or 

 one-third of the total sugar. 



On the basis of experiments, which we cannot go into more 

 fully here, E. DUBOURG (I.) formed the conclusion that yeasts can 

 be induced, by habituation, to utilise certain sugars that they are 

 normally incapable of attacking. A yeast, for instance, that is 

 unable to invert saccharose may acquire this capacity by being 

 grown in a mixture of glucose and saccharose, and then trans- 

 ferred to a solution of saccharose containing suitable yeast foods. 

 Unfortunately, the yeast was not properly identified in the report. 

 A. KLOCKER (IV.) repeated Dubourg's experiment with a number 

 of yeasts characterised by the peculiarity in question, among them 

 being the one with which we are more particularly concerned at 

 present, namely, Sacch. apiculatus (see p. 259, vol. ii.). The results, 

 however, were entirely negative, our budding fungus being unable 

 to ferment saccharose after this preparatory treatment and there- 

 fore contrary to Dubourg's hypothesis incapable of secreting 

 invertase. 



Despite the initially rapid reproduction of Apiculatus yeasts 

 in grape and fruit juices, the fermentation they induce produces 

 but little alcohol, proceeds slowly, and therefore usually extends 

 over a considerable period of time. This is evident, for example, 

 from the series of experiments recounted by MULLER-THURGAU 

 (XI V.). At 14 C., the quantity of carbon dioxide liberated 

 amounted, during the first ten days of fermentation in grape 

 juice, to 6.8 grms. per litre; in 20 days, 9.4 grms. ; in 40 days, 

 12 grms. ; in 80 days, 14.6 grms. ; in 100 days, 15 grms. ; in 

 130 days, 16.8 grms.. and in 205 days, 18 grms. ; consequently the 

 Apiculatus races are all weak ferments, though differing con- 

 siderably in relative degree. Under ordinary conditions of fermen- 

 tation, the quantity of alcohol finally produced (see p. 426, vol. ii.) 

 by the races hitherto described varies between 2.5 and 4.5 per 

 cent, by weight ; though two of the races recently tested by the 

 writer formed 6 per cent, of alcohol from grape juice. The final 

 content of alcohol also differs correspondingly in pear juice and 

 grape juice, even when the same yeast is employed in both cases, 

 Miiller-Thurgau having found ih&t Apiculatus race 8, for instance, 

 furnishes 2.8 per cent, of alcohol in grape juice, as compared with 

 3.5 per cent, in pear juice. It may be assumed that with this 

 budding fungus, as with others, the activity as well as the growth 

 of the individual cells will be influenced by the conditions of 

 nutrition and general environment, the relative speed of fermen- 

 tation and the attenuation obtained with liquids of different 

 constitution being affected both by the number of active yeast 

 cells and the fermentative activity of the individual cells. It is, 



