903 
and cannot be well recognised on account of the opaqueness of the 
medium. Yet I have further examined these colonies by making 
streaks of them on broth-agar plates, always finding that they more or 
less readily develop; colonies failing in this respect I did not find. 
[ have also tried to obtain anorganic denitrifications with those 
portions of the streaks on the sulfur- and thio-sulfate plates lying 
between the colonies, but as well in aërobic as in anaërobic condi- 
tion always in vain. Neither microscopically nor by colouring, bac- 
teria or microbes of other nature could be found in these parts. 
Hence it follows with certainty that tle agents of the anorganic 
denitrification grow to colonies both on the sulfur-chalk and the 
thio-sulfate plates and besides, as will be still further proved below, 
on the ordinary broth plates. The highly improbable hypothesis that 
they might be obligative anaérobes is disproved by these experiments, 
which are, however, well in accordance with the conception that 
by growth on organic matter their power of autotrophy gets lost. 
To compare the broth with the thiosulfate medium I made the 
following experiment. 
A platinum wire was bent so as to form at one end a loop, with 
which droplets of the same size could easily be taken up; the other 
end was curved to a circular base, which made it possible to place 
it on the balance and determine the weight of the droplet. Now 
drops of equal size were taken up with this loop from the anorganic 
denitrifications and transported for comparison to a thiosulfate- and 
to a broth-plate. The result was that the number as well as the 
species of the developing colonies were about the same. All the 
colonies grown on the thiosulfate plates, after being sown on broth- 
plates, developed very well, quite in accordance with what was 
observed already for the colonies grown on the sulfur-chalk plates. 
So it is certain that the microbes causing the anorganic denitrifi- 
cation produce colonies on the organic plates. 
This statement is of particular interest as the colonies, when 
again transferred to the anorganic sulfur-chalk mixture, do not, or 
only very feebly, denitrify, which means that they have almost or 
quite lost their power of chemosynthesis *). 
This is not only true for the pure colonies separately, but like- 
wise for the combinations that may be made of them. Even when 
the whole bacterial mixture on the plates is transported to the anor- 
ganic medium, only a slight or no chemosynthesis or denitrification 
‘) In “Untersuchungen über die Physiologie denitrifizirender Schwefelbakterién, 
Silzungsberichte Heidelberger Akademie. Biol. Abt. 1912", R. Lieske has come 
to another result. 
