125 
It was supposed that the observed alteration in the mould film 
might be explained by mutation, which was proved true by the 
biological method. By isolation on malt gelatin two forms could be 
obtained from these cultures. One of these was very lightly coloured 
in consequence of the small number of spores. This form will be 
indicated as “the mutant”. The other had preserved the dark green 
colour and had evidently remained identie with the original culture. 
The difference between the two forms was very marked. 
So it cannot be doubted, that at prolonged cultivation in presence 
of p-oxybenzoie acid mutation does indeed take place. With proto- 
catechetie acid as carbon food the same was observed. Furthermore, 
Table 1 shows that salicylic acid and trichloracrylic acid promote 
this process. 
In the floating mould layer the extent of the mutant was greatest 
in those flasks where the said antiseptica were most concentrated. 
At a continued cultivation on malt agar the thus obtained mutant, 
which in all the said cases seemed the same, remained constant. 
If the mutant and the original form were again transferred to a 
p-oxybenzoie acid solution with the anorganie food named in the 
table, they also preserved their properties. 
Under the microscope the mutant produced considerably fewer spores 
than the primitive form *) and its mycelium had a greater tenacity, 
which was repeatedly stated. 
There was besides a peculiar difference in smell, as the original 
form gave out the well-known “mould odour’, which the mutant 
did not. : 
The growth of the mutant on para-oxybenzoic acid was considerably 
slower than that of the primifive form. 
In the laboratory a third form of Penicillium glaucum was present, 
distinguished from the original form of my experiments by darker 
green spores and which served for the subsequent experiments. 
It was first cultivated during four days on p-oxybenzoic acid 
where the growth was very slow; “it was then transferred to a 
new flask with the same medium, and now the growth was much 
accelerated, which proved that in these few days accommodation 
to the para-oxybenzoic acid had taken place. Furthermore it was 
observed that also here, after a prolonged cultivation on p-oxybenzoic 
acid mutation occurred. Substances such as tetrachlor-propionamid 
CHCI,CCl,C=0 \ and pentachlor-propionamid/CCl,—Cvl,—C=0 ), 
Swi) ( Swit) 
1) Whether the difference in the number of spores was accompanied by a 
difference in intensity of colour is not settled as yet. 
g* 
