OXYGEN FROM COLOURED BACTERIA. 149 
distinct yellowish or brownish tinge, which +H,SO, or HCl 
turns emerald and finally bluish green, showing etiolin to be 
present. The green residue, on treatment with water or alcohol, 
yields up a bright emerald or deep bluish-green pigment=alka- 
chlorophyll. 
The colourless bacterial residues after extraction with alcohol 
were tested for cellulose and starch, but neither could be detected. 
The assimilatory product is therefore not starch, but is probably 
sugar, 
The chlorophyll, whether extracted as alkachlorophyll or as 
chlorophyllan, when exposed to light in the presence of oxygen, 
becomes in an hour or two olive-green, and then commences to 
fade, in 4-12 hours is quite yellow, and in 2-3 days is almost or 
entirely colourless. In darkness it remains green longer. The 
rapid fading may be due to the presence of some organic sub- 
stance extracted either from the bacterium itself or from the 
stagnant water. 
Both of these green Bacteria therefore possess normal chloro- 
Phyll and are able to assimilate. They grow only in stagnant 
water, exposed to light, in which a little decomposing vegetable 
material is or has been present. They can grow in water in 
which no more than a mere trace of oxygen can possibly be 
Present. If introduced into water containing inorganic salts 
ei growth takes place, and the Bacteria soon fall to the 
morem and die. Bacillus virens may show a weak power of 
neve "hel » but the AMicrococcus-form is non-motile. It can 
layers of "n when living, distribute itself through the different 
a given ] x water in which it is growing and maintain itself at 
adapting ite This 18 evidently due to its possessing a power of 
around it. specific gravity to that of the fluid immediately 
wow ge l kept in darkness the Bacteria retain their green 
and settle han as two weeks, but gradually sink to the bottom 
leaving a clear Ate evidently also much diminished in amount, 
deposited " uid above. On microscopical examination the 
and evid &reen film is seen to be composed largely of colourless 
"ently dead forms. On bringing such cultures which have 
veen for three week Inging | , 
s or longer in the darkness into light again 
a Week or go the fluid . tai 
the same gree b ul becomes green and is found to contain 
tubes al a acterium as was present previously. In sealed 
ong with a little hydrogen in darkness, the Bacteria 
