126 
likewise compounds which retard the growth, again favoured the 
mutation, so that this process seems rather general. 
The smaller number of spores and the less rapid growth evidently 
lead to explain the properties of this mutant by a loss of character- 
istics or gens. *) 
B. Aspergillus niger. 
We started for this investigation from a pure culture of the la- 
boratory collection, which was first cultivated some time on a 2°/, 
suecinie acid solution. In several inoculations in ERLENMEIJER-flasks 
with different culture media, a considerable alteration of this black 
mould occurred. 
Using a 2°/, solution of galactose it was observed that in this 
medium, beside the primitive form with black spores, a brown and 
a white one appeared, which three forms may be called I, II, 
and II. 
On a 2°/, rhamnose solution of for the rest the same composition 
(tapwater, 0,05°/, NH,Cl, 0,05°/, KH,PO,, 0,02°/, MgSO,) the black 
and the brown forms (1) and (II) were distinctly present, the white 
form (III) wanting. A tube, to which beside the food consisting of 
0.3°/, p-oxybenzoic acid, 9 mgr. (per 50 c.c.) dichloraerylie acid 
‘CH=CCI—C=0 had been added, showed after about a month 
La < 
a quite brown mould layer. Later experiments proved that in nutrient 
solutions with 2°/, glucose as source of carbon, under the influence 
of 1°/, boric acid likewise mutation occurs. 
The three forms from the galactose solution were isolated on 
malt agar; II and II distinctly gave fewer spores than I, and Ill 
fewer than II. They were transferred to media of tapwater-agar to 
which beside 0,05 °/, NH, NO, and 0,05 °/, KH, PO,, 2 °/, galactose 
was added. On this plate the appearance of the mutants was different 
from that on the malt agar. From this galactose plate I, II, and HI 
were again transferred to malt agar; the latter cultures were used 
for the examination of the plastic aequivalent of the carbon, where- 
unto we return below. 
It was clear under the microscope that besides a smaller quantity 
of spores, there was also a decrease of colour intensity of these 
spores in IL and HI, which had become brown instead of black. 
The question whether III might also be obtained without any spores 
B) Compare M. W. Bevertycx, Mutation bei Mikroben. Folia Microbiologica, 
1912, p. 5. 
