38 
Messrs Parvis and Warwick, The Influence of 
18 March. 
9.30 a.m. No light. Cells granular; faint indications of spores. 
White light. Faint indications of spores. 
Green light. Faint indications, slightly less than in no light. 
Blue light. Less marked indications of sporulation than in 
the green. 
1.30 p.m. No light. Strong indications of spores. 
White light. Indications in a few cells. 
Green light. Not so far advanced in sporulation as in white 
light, and less than in no light. 
Blue light. No advance on the observations at 9.30 a.m. 
9.15 p.m. No light. Very slight advance on the observations at 
1.30 p.m. 
White light. The sporulation was nearly as far advanced 
as in no light. 
Green light. Sporulation not so far advanced as in white 
light. The cells appeared to be more empty looking. 
Blue light. Indications of spores were exceedingly slight ; 
cells very empty looking. 
19 March. 
9.20 a.m. No light. Not examined. 
White light. About 25 °/ 0 of the cells had sporulated. 
Green light. A certain number of the cells had developed ; 
some of the unsporulated cells looked very empty ; and 
the spores of others were very small. 
Blue light. The development was not unlike that in the 
green ; the spores were remarkably small, and the non- 
sporulated cells very empty looking. 
5.30p.m. No light. Well marked advance in sporulation; some of 
the cells had perfect spores. 
White light. About 60 — 7 0 °/ 0 of the cells had sporulated, 
and the remainder were very empty looking. 
Green light. About 50 °/ 0 of the cells sporulated ; the rest 
were somewhat empty looking. 
Blue light. Sporulation very similar to that in the green ; 
the non-sporulated cells were very empty looking. 
The results of these experiments with an ordinary English 
yeast are similar to the previous ones, viz. : that the rays of 
greater refrangibility interfered with the development of the 
spores, and that the green and blue rays influenced the retarda- 
tion more than those of lower refrangibility. 
A few experiments were conducted with the Cerevisia3 and 
Pastorianus species before-mentioned, by placing them within the 
influence of the ultra-violet rays. The light issued from an un- 
covered Welsbach mantle and played directly on the surface of 
the seeded gypsum blocks in one series, and through quartz 
