558 Hansen. — Experimental Studies on the 
brewery-fermentations. But, if we ask, what do we know 
about this variation which is supposed to have taken place 
from the primitive form, then the answer must be : Nothing at 
all. We have never been able to carry one single S accharomyces 
species back to its progenitor ! Some years ago I showed, it is 
true, that typical Saccharomycetes may appear in forms resem- 
bling Oidium and Dematium , and possessed of a mycelium 
with distinct transverse septa, but we have not advanced 
further in that direction. As is well known, Takamine, Juhler 
and Jorgensen have recently come forward as advocates of the 
view formerly represented, especially by Bail and Hoffmann, 
that the Saccharomycetes are merely developmental phases of 
various common mould-fungi, and they have also all three 
fallen back upon the idea alluded to above, that there should 
be a possibility of obtaining, through the original forms, yeast- 
species that in certain particulars might be better than those 
actually employed. In their cultivations they started from 
the moulds themselves, and describe how Aspergillus and 
Dematium develop S accharomyces- c ells . 
Klocker and Schionning at the Carlsberg Laboratory 
repeated the above experiments with Aspergillus Oryzae , 
and in accordance with the previous investigations of Cohn, 
Biisgen and Wehmer, they were not able to observe any 
development of yeast-cells. The whole question must at 
present still be considered as an open one. For the rest we 
know now so many mould-fungi that develop alcoholic fermen- 
tation-fungi, that it would not be a matter of wonder if some 
should really be found which also develop yeast-cells with 
endospores. (About this question see the articles of Juhler, 
Jorgensen, Wehmer and myself in Centralblatt f. Bakterio- 
logie, 2 te Abt. 1895, pp. 16, 65, 321, 326, and 565.) 
In the preceding portion of my paper I have chiefly 
described the phenomena of variation without inquiring more 
closely into its mechanism, nor have we examined the agencies 
and causes to which it is due. I have, however, made ex- 
tensive experiments in that direction also, but to describe 
the details of these would on this occasion lead us too far. 
