Spectral Colours on the Sporulation of Saccharomyces. 37 
due to the light being much less intense in this series of 
experiments. And besides that, the slow advance of the sporu- 
lation in the cells cultivated in the dark shewed that the cells 
were not very vigorous and healthy at the beginning. 
The following notes describe the fourth series with pure 
cultures of S. Cerevisice I. 
3 March. 
11 a.m. The gypsum blocks were seeded. 
4 March. 
10.15 a.m. Red light. Most of the cells shewed indications of sporu- 
lation. 
Green light. A few cells shewed doubtful indications. 
Blue light. There were no indications whatever. 
White light. Shewed indications as in red and no light. 
No light. Shewed indications as in red. 
2.45 pan. Red light. Sporulation advanced since morning. 
Green light. Hardly any advance. 
Blue light. No indications whatever. 
White light. Slightly less advanced than in the red and no 
light. 
No light. Sporulation as in the red light. 
7 p.m. Red light. Marked advance in sporulation. 
Green light. Some advance, but the spores had an empty 
appearance. Not so advanced as in white light. 
Blue light. A very few cells seem to be forming spores, 
but they were very empty looking, and other cells were 
deteriorating. 
White light. Slightly less advanced than in red. 
No light. Sporulation as in the red light. 
The conclusions to be drawn from this fourth series of experi- 
ments confirm the previous series, viz.: (1) that the red rays 
appeared to act in the same way on the sporulation as when 
the yeast was left to sporulate in the dark, (2) that the green 
rays retarded the sporulation, and (3) that the blue and violet 
rays retarded the sporulation still more markedly. Only very 
vigorous and healthy cells seem to be able to sporulate under 
the influence of the blue and violet rays. 
In the following fifth series an ordinary English brewery yeast 
was employed, and the observations were confined to the cultiva- 
tions under the influence of no light, white light and green and 
blue lights. 
17 March. 
9.30 a.m. The gypsum blocks were seeded. 
