130 
IOWA ACADEMY OF SCIENCES. 
Medium with the Addition 
of Glucose 
Reaction. 
Color. 
No. 1 
No. 2 
C:Tieck 
Alkaline 
Orange-red. 
Carmine to violet. 
.1 per cent 
Neutral 
No. 3 
1 per cent 
Faintly acid 
Red-violet, big growth. 
No. 4 
2 per cent 
Faintly acid 
Red-violet, big growth. 
No. 5 
3 per cent 
Acid 
Violet with some white. 
White. 
No. 6 
4 per cent 
Acid strongly 
No. 7 
5 per cent 
Acid strongly 
White. 
No. 8 
6 per cent 
Acid strongly 
White. 
No. 9 
7 per cent 
Acid strongly.. 
No growth. 
He made a study of B. ruber halticus, the so-called Kiel 
water bacillus. Schotellius by growing the organisms at 
higher temperatures obtained colorless colonies. But these 
varieties are inconstant and further cultures in nutrient 
media cause the organism to take on color. Migula 
refers to these as forms rather than varieties. Laurent 
made careful investigations and arrived at the following 
conclusions: 
That B. ruber balticus on certain media produces acid 
material, and on others, alkaline. 
That high temperature is unfavorable for production of 
color. 
That colorless forms may be obtained through culture 
in direct sunlight on strongly acid and strongly alkaline 
media. 
When grown on potato at 35° C. the violet color disap- 
pears. If the culture is allowed to stand for one day at 
18° C. it becomes carmine red. At 35° C. it becomes violet 
upon addition of HCl. Saltz is sure that the violet color 
is intensified. 
It follows from his results that in cultures kept at high 
temperatures the breathing powers of bacteria and the 
production of carbon dioxide is favored, and carbon dioxide 
favors production of violet pigment. According to Milburn 
the production of violet color is infiuenced through the 
action of the medium. When it is acid the violet color is 
produced, when alkaline an orange red color appears. 
To show the effect of light on the chromogenisis of B. 
violaceous, six agar slants were inoculated. Then they 
were exposed to the direct rays of the sunlight: — 
