desired end, which is the comparative study of the same
mycoderma on the surface and in the depths.

"Never again," continues Pasteur, "did I see the
yeast or an active alcoholic fermentation, following the
submersion of the flowers, either in the flasks or in the
matrasses connected with these flasks. . . . At a time
when ideas on the transformation of species are so
easily adopted, perhaps because they dispense with
rigorous experimentation, it is not without interest to
consider that in the course of my researches on the culture
of microscopic plants in the pure state, I have once had
occasion to believe in the transformation of one organism
into another, in the transformation of the Mycoderma vini
or cerevisiœ into yeast, and that, this time, I was in
error. I did not know how to avoid the cause of error
which my justified confidence in the germ theory
had led me to discover so often in the observations of
others."

The same flask with two tubulures served Pasteur to
show that the alcoholic yeast is not transformed into a
lactic ferment, as J. Duval said, nor into Penicillium or
Aspergillus, as Hoffmann maintained; that this yeast,
itself, did not come from the transformation of the
spores of Penicillium, as Trécul said; nor furthermore
did the Mycoderma aceti yield the bacteria which
Béchamp believed he saw derived from it. In short,
the idea of species was saved for the time being from the
attack which was directed against it, and it has not
been contested seriously since that time, at least on this
ground.

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