556 Hansen. — Experimental Shidies on the 
tend to prove the same. Later, Effront, in his well-known 
experiments on hydrofluoric acid and alkaline fluorides, arrived 
at the same general result. In all these cases only transitory 
transformations are meant. 
In the foregoing I have mentioned that a great part of my 
experiments were carried out to determine the influence which 
temperature has in respect to the form and the functions of 
yeast-cells ; by this I was also led to make the following 
researches on the attenuation of the fermenting powers of 
yeast-cells. Carlsberg bottom-yeast, No. i, was cultivated in 
wort at 3 2° C. through eight cultures in such a manner that 
each subsequent culture was inoculated from a foregoing one, 
and left standing at rest until the fermentation had ceased, 
without being aerated. In the ninth culture a variety was 
obtained, which gave 1-2 per cent, of alcohol less than its 
primitive form, when the fermentation was carried out in wort 
(14 per cent. Ball.) to which was added 10 per cent, of sac- 
charose. Also in other directions changes had taken place ; 
thus the new variety in some brewery-experiments clarified 
better and gave a more feeble attenuation at the end of 
the primary fermentation than the growth from which it 
descended. The variety seems to be constant, and what has 
been found out for the species in question seems also in the 
main to hold good for others. 
But if the same species was submitted to the same treat- 
ment, only with the difference that the growth was strongly 
aerated and renewed every day, these transformations would 
not occur; they thus afford an illustration of the fact, that 
temperature only under certain conditions has the effect 
described. 
Before concluding this survey of the varieties observed by 
me, I have to record an experiment by which the effect of the 
chemical composition of the nutrient liquid is shown. Sac - 
charomyces Pastorianus I., is one of the disease-yeasts of beer, 
to which it imparts an offensive odour and a disagreeable 
bitter taste. According to Mach and Portele’s investigations, 
however, it gives a good wine, and my own experiments have 
