TRANSFORMATION OF ONE SPECIES INTO ANOTHER 197 



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 virii 

 or cerevisine 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 HofTmann maintained; that this yeast, 

 itself, did not come from the transformation of the 

 spores of Penicillium, as Trecul said; nor furthermore 

 did the Mycoderma aceti yield the bacteria which 

 Bechamp 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. 



