420 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
reasoning is based, by supposing that the chlorophyll grains, 
normally accustomed to an abundant oxygen supply, are readily 
affected and soon killed by the deficient supply of oxygen, 
whilst the protoplasm, being more resistant, remains living and 
streaming. This, though partly true, is only a partial explana- 
tion. The condition first produced in the chlorophyll grain is 
one of inanition, characterized by an inability to assimilate, but 
from which recovery is possible. If the exposure goes too 
far, the chlorophyll grains are killed and lose their power of 
recovery, and this is quickly followed by the death of the entire 
cell. 
That even in Chara a supply of external oxygen is not always 
necessary for the recovery from inanition is shown by the fact 
that end cells of Chara which had temporarily lost the power of 
assimilation, if kept in carefully closed cells under water exposed 
to light, recovered and recommenced to assimilate. 
If preparations of Chara are kept in closed cells thinly ringed 
with vaseline in the darkness,in many cases the end cells remain 
living and show distinct though slow rotation for many days, 
and in certain cases for as long as five weeks, though exposed to 
light for less than one minute each week. No loss of water 
takes place from such acell; Bacterium Termo, if enclosed, comes 
to rest in a few minutes, and as the ringing remains intact it is 
difficult at first to explain the phenomena observed, for here 
apparently the rotation of Ohara continues in the absence of 
oxygen for as long as several weeks, which is in direct contra- 
diction to the results obtained in an atmosphere of hydrogen. 
It does not follow that because Chara in an atmosphere of 
hydrogen ceases to show rotation and finally dies, that therefore 
this effect is produced by the absence of oxygen, for it might 
readily be due to a direct action of the hydrogen itself. If, 
however, the preparations are carefully and thickly ringed with 
a mixture of vaseline and wax, or vaseline and paraffin, or if a 
considerable quantity of living Bacterium Termo is enclosed, in 
two or three days the end cells cease to show rotation and die. 
Spirilla and Monas Termo, for the movement of which the 
presence of the minutest trace of oxygen suffices, continue to 
move in thinly ringed preparations as above for an indefinite 
length of time, whereas in thiekly ringed cells they cease to 
move in a few hours. Through the vaseline in the thinly ringed 
preparations, therefore, a trace of oxygen diffuses, and this is 
