MR. A. J. EWART ON ASSIMILATORY INHIBITION. 421 
sufficient to cause the movement of Spirillum and the rotation 
of Chara to continue, but is insufficient for the movement of 
Bacterium Termo. 
Preparations of Chara, thickly ringed with a mixture of 
wax and vaseline and kept immersed in cold boiled oxygenless 
water in closed bottles in the darkness, gave the following 
results :— 
After All end cells living. In half no rotation, in rest slow creeping 
20 hours. rotation. After a few minutes exposure to light, rotation 
quickens in those cells where it was previously present, and 
a weak evolution of oxygen is shown. In some cases a weak 
but distinct evolution of oxygen is shown before rotation 
commences. After 15 to 30 minutes’ exposure to light, both 
rotation and assimilation are fairly active. 
After Most end cells are still living, but no rotation or assimilation 
30 hours. is shown. Rotation soon returns on exposure to light, but 
assimilation mostly not for an hour or two. In some cases 
no recovery at all takes place. In a few cases slow rotation 
is shown after exposure to light, but assimilation does not 
recover and, later, rotation ceases and the cells die. 
After | All cells are fatally affected and have lost the power of re- 
40 hours. covery. 
In an atmosphere of hydrogen in the darkness all rotation 
ceases in Chara in about 8 or 10 hours, and in a current of 
bydrogen exposed to light is in from 10 to 14 hours extremely 
slow or absent. In a current of hydrogen, oxygen is continually 
being forcibly withdrawn from the filaments, as is shown by the 
fact that, when suddenly surrounded by an atmosphere of hydro- 
gen, the filaments give off oxygen more rapidly than before, causing 
an increased activity of the movement of the surrounding Bacteria, 
and continue to do so for some time, especially if exposed to 
light. In the closed cell surrounded by oxygenless water, on the 
other hand, rotation stops, solely because all supply of oxygen 
from without is cut off, and ceases only when all stored intra- 
molecular oxygen has been used up and the protoplasm has been 
reduced to its lowest possible condition of deoxidization. 
If preparations of end cells of Chara are exposed to light in 
a hanging drop with B. Termo in a gas-chamber filled with pure 
CO,, in about 10 minutes all evolution of oxygen * ceases, but 
* B. Termo, in a hanging drop over an atmosphere of CO, containing a trace 
of oxygen, continue to move fairly actively, though after prolonged exposure 
the movement is weakened and finally stops. 
