554 Hansen . — Experimental Studies on the 
which had lost their power of spore-formation, I found that, 
when placed in the earth, they showed a decreased vitality as 
compared with their original forms, and generally perished 
within less than a year. In the sugar-solutions, on the other 
hand, in which they had produced alcoholic fermentation, 
they kept alive for several years, and, as far as my experi- 
ments go, they appear not to be second to their parent-cells 
in this respect. 
Since the varieties no longer possess the power of forming 
films on the surface of liquids, their life in these becomes quite 
different from what it used to be. As shown in one of my 
papers, the cells of the film which develops on fermented beer- 
wort cause the liquid to become lighter in colour; and from 
the chemical investigations of Kruis and Rayman (1891) we 
know that these cells produce a vigorous oxidation, by which 
the alcohol is converted into carbonic acid and water. Thus 
the yeast, as long as it is in its normal state, not only produces 
alcoholic fermentation in the sugar-liquid in which it is present, 
but when it has carried this fermentation as far as it is able 
to do, it forthwith takes to transforming the alcohol produced 
by itself, thus coming to live in a liquid with less and less 
of alcohol. The varieties not being able to develop any film, 
they of course have given up this activity. As an example of 
the contrast between the varieties and their original form in 
this respect, I will here only mention the result of one of my 
experiments. Two cultures in the same wort, of which one 
contained a brewers’ bottom-fermentation yeast, the other 
a variety of the same, which I had produced in the manner 
described above, were left to stand for six months. The 
original form had developed a film as usual, and its fluid 
contained only 1*5 per cent, (by volume) of alcohol, whilst the 
variety showed 5-5 per cent., that is, the same amount of 
alcohol as it contained after standing the first month. The 
beer from the primitive form was lighter in colour than the 
corresponding beer from the variety. Thus the varieties 
described manifest in those directions also sharp differences 
from their primitive forms. 
