Spectral Colours on the Sporulation of Saccharomyces. 39 
plates in another series. It appeared that the development of 
the spores was retarded still more than when they were under 
the influence of the blue and violet rays. And the general effect 
was to cause the cells to appear very thin and empty looking, as 
if they were breaking down. 
Influence of radium. Finally the action of the emanations 
from radium was observed on four separate cultures of Cerevisise. 
The times of exposures were 15, 30 and 60 minutes and 30 hours 
respectively. The radium salt, kindly lent to us by Mr W. B. 
Hardy, was placed alternately over the seeded gypsum blocks. 
On examining the culture of 15 mins, exposure, the cells were 
granular ; in the culture of 30 mins, exposure the cells were more 
marked in their granulations ; whilst in that of 60 minutes the 
cells were very granular, and the contents of a few of the cells 
appeared to be escaping, due to the break-down of the cell wall. 
The granulation of the protoplasm of the cells of Saccharomyces 
is always a sure sign of starvation, decay, and old age, and it 
does not normally develope in so short a time as 15 minutes. 
In the culture of 30 hours exposure many of the cells appeared 
to have burst and the contents escaped. The cultures were after- 
wards incubated normally in order to develope spores. There 
appeared to be indications of spores here and there : but on 
inoculating sterilised wort from each of the growths, no fer- 
mentation or development of the cells was obtained. It appeared 
as if the radium emanations had destroyed the vitality of the cells. 
General Conclusions. 
The more important conclusions to be drawn from the pre- 
ceding observations are: (1) the red rays or rays of low re- 
frangibility accelerated the formation of spores more quickly than 
when the cells were incubated under the influence of white light ; 
and they appeared to stimulate the activity of the sporulation 
more quickly than when the development took place in the dark, 
although in the latter case the sporulation seemed to be com- 
pleted at about the same time as that in the red ; (2) the green 
rays appeared to retard the development of the spores ; (3) the 
blue and violet rays retarded the sporulation more markedly than 
the green rays ; and (4) the ultra-violet rays were still more 
effective in the retardation, and they appeared to have the further 
effect of influencing detrimentally the vitality of the cells, when 
the latter were exposed to their influence for some time. 
