OXYGEN FROM COLOURED BACTERIA. 131 
indeed it persists slightly longer in darkness than it does in 
light. 
Thus preparations exposed to sunlight, but kept cool by being 
floated on water, cease in 1-2 hours to evolve oxygen; whereas 
similar preparations after being exposed to diffuse daylight for 
8 hours showed a weak evolution of oxygen, which in prepara- 
tions kept in the darkness for the same time was still moderately 
active. 
Ifthe dark heat-rays from a large flask filled with hot water are 
collected and thrown upon gelatine preparations, when the evolu- 
tion of oxygen is already fairly active, no further increase can be 
detected. When, however, the evolution of oxygen is very faint 
or has almost ceased, a distinct increase or recommencement of 
the evolution of oxygen lasting for a short time may be shown. 
The further study of the influence of external radiation upon 
the evolution of oxygen was carried out by the gas-chamber and 
hanging-drop method. The microscope was isolated upon 4 
clay dish, through which the tubes passed, and was covered by 
cylinders of metal, cardboard, clay, &c. After hydrogen has 
been passed through the time that elapses, when the preparations 
are exposed to light, before the Bacterium Termo in the hanging- 
drop Tecommence to move is noted and the time when they are in 
active motion. A cover is now placed over the microscope and 
4 current of H is passed through for the time necessary to 
bring the B. Termo again completely to rest, when the tubes are 
clamped and the time noted. After a time the cover is removed 
and the hanging-drop at once examined. In this way the times 
necessa ry for B. Termo to recommence to move under the given 
conditions is found, and this represents the relative rates at 
maich oxygen is evolved under these conditions. By this means 
"hin definitely established that the evolution of oxygen was 
nisl E ent of all external radiation, that it is slightly accele- 
y the dark heat-rays, but when so accelerated ceases 
Correspondingly sooner, 
" M Bacteria are heated to 100? C. and then mounted, 
or in "s of O is shown. Preparations kept at 30? C. in light 
which in 9 » prow at first a very active evolution of oxygen, 
Preparations x ours, however, entirely ceases; whereas similar 
light stil) S kept at 20° O. in darkness or exposed to diffuse 
show a weak but distinct evolution of oxygen. At 
x 2 
