338 
ROBERT AARON STEINBERG 
placed aside as unfit for further use. The practise was also followed of pre- 
serving a single duplicate stock culture, unused, from each transfer. The 
numbers given with the designation of the strain refer to the total number 
of transfers since the original isolation of the strains. 
I present here summaries of three of the i8 experiments presented in the 
4. The effect of adding zinc to the culture medium (strain W). Strain W, 6. Each value 
the average of five duplicate cultures. 
Mg. Zn/L 
Yield 
Sporulation 
Mg. Zn/L 
Yield 
Sporulation 
0.136 g. 
Excellent. 
5-0 
0.963 g. 
Sterile, 
O.OI 
0.287 
10. 0 
0.906 
O.I 
0.851 
Good. 
15.0 
0.902 
0.5 
0.843 
Moderate. 
20.0 
0.901 
I.O 
0.915 
25.0 
0.945 
5. The effect of adding zinc to the culture medium (strain Y). Strain Y, 6. Each value 
the average of five duplicate cultures. 
Mg. Zn/L 
Yield 
Sporulation 
Mg. Zn/L 
Yield 
Sporulation 
0.205 g. 
Excellent. 
0.757 g. 
Good. 
o.oi 
0.283 
10. 0 
0.771 
O.I 
0.823 
15.0 
0.746 
Fair. 
0.5 
0.826 
Good. 
20.0 
0.725 
1.0 
0.859 
25.0 
0.754 
6. The effect of adding zinc to the culture medium (Strains W and Y). 
Each value the average of two duplicate cultures, except the controls which are the 
average of five duplicate cultures. 
Strain W, lo 
Mg. Zn/L 
Yield 
Sporulation 
Methyl Violet 
0.177 g. 
Excellent. 
Blue. 
0.01 
0.287 
0.02 
0.381 
0.03 
0.475 
0.04 
0.523 
Green-blue. 
0.05 
0.534 
0.06 
0.688 
Blue-green. 
0.07 
0.697 
0.08 
0.758 
Green. 
0.09 
0.761 
O.IO 
0.800 
Strain Y, lo 
Mg. Zn/L 
Yield 
Sporulation 
Methyl Violet 
0.222 g. 
Excellent. 
Blue. 
O.OI 
0.440 
Green-blue. 
0.02 
0.501 
0.03 
0.563 
Blue-green. 
0.04 
0.642 
0.05 
0.707 
Fair. 
Green. 
0.06 
0.793 
0.07 
0.753 
Practically sterile. 
0.08 
0.734 
0.09 
0.770 
O.IO 
0.799 
