OXYGEN FROM COLOURED BACTERIA. 129 
in 13 to 2 hours, whereas with an equal bulk of the coloured 
Bacteria this takes place in 1 hour. The green alge exposed to 
light in an atmosphere of H also cause the Bacteria in a hanging- 
drop of Bacterium Termo to move rather actively in 3-5 minutes ; 
but if the H used contains a little CO,, or if an equal bulk of 
coloured Bacteria is used, the B. Termo commence to move a 
minute or two sooner. 
The evolution of CO, in an atmosphere of H. by the coloured 
Bacteria can also be demonstrated by the precipitation of BaCO, 
in a hanging-drop of BaH,O,, and by the partial or complete re- 
dissolving of freshly precipitated CaHPO,. After being in the 
chamber in an atmosphere of H for as long as 24 hours, a 
mass of Bacillus brunneus may still be able to evolve traces of 
CO,, though all evolution of oxygen has long since ceased and 
no external supply is present. 
In gelatine preparations or in the chamber in H, the evolution 
of oxygen does not continue for an indefinite length of time, 
but sooner or later ceases. Where the evolution of oxygen is 
weak it generally ceases in 2-3 hours (Sarcina lutea, Diplococcus 
roseus, &c.), but where it is stronger (Bacillus brunneus, &c.) it 
generally continues for 5-6 hours, and in some cases a faint 
evolution of oxygen may still be shown after 10-12 hours. 
This gradual diminution and final cessation of the evolution 
of oxygen might be due to the Bacteria being gradually more 
and more injuriously affected. A mass of Bacteria, however, 
which has ceased to evolve oxygen in the gas-chamber in hydrogen, 
after being re-exposed to air for some time, may again show a 
distinct evolution of oxygen, though weaker and of shorter 
duration. It is possible that this phenomenon might be due 
to the induction of a condition of assimilatory inhibition 
from which on re-exposure to air recovery takes place, and 
which corresponds to the condition of inanition which is finally 
induced in Ohara when kept in an atmosphere of H, and from 
which on exposure to air a more or less rapid recovery may take 
place. 
The fact that these coloured Bacteria grow and develop quite 
normally on agar or gelatine cultures and form their pigment in 
the darkness, is no argument against their possessing an assimila- 
tory pigment and being also able to assimilate as green plants do ; 
for many plants can form chlorophyll in the darkness, and all can 
form etiolin, whilst Beyerinck has shown that it is possible to 
LINN. JOURN.—BOTANY, VOL. XXXIII. LI 
