148 DR. A. Je EWART ON THE EVOLUTION OF 
can only be detected by Spirillum. Engelmann calls the Bac- 
terium Bacterium chlorinum, but it is probably the same form 
previously described by Van Tieghem as B. viride. Scarcity of 
material and the impurity of the water-cultures prevented 
Engelmann from extracting the pigment or examining it spectro- 
scopically. 
Ina glass cylinder containing mud and stagnant water and 
exposed to diffuse daylight, the water became turbid and green 
to yellowish green in colour. Microscopical examination revealed 
the presence of an exceedingly numerous JMicrococcus-form, 
occasionally isolated or in clumps, but generally forming irregular 
or twisted chains of generally 2-12, and more rarely 12-30, indi- 
viduals. Examination with high powers showed the plasma of 
the bacterium to have a distinct greenish tinge. A very few 
other, but uncoloured, Bacteria were present, but no other green 
organism. 
Later, in another culture a green Bacillus-form having the 
power of forming endospores, and corresponding in all respects 
with the Bacillus virens of Van Tieghem, was found. By means 
of Spirillum the power of these Bacteria to evolve oxygen when 
exposed to light could readily be demonstrated. The Micro- 
coccus-form frequently formed large loose green flocks adhering 
to the sides of the cylinder. These gave almost perfectly pure 
masses of the green Bacterium. Portions of such, moun 
either directly in water or in a little thin gelatine, showed at the 
edges an evolution of oxygen sufficiently strong to keep B. Termo 
in moderately active movement and ceasing in a few seconds to 
a minute in the darkness. 
The extraction of the pigment could either be made from such 
material, or from the water in which the Bacteria were floating 
and which microscopical examination showed to contain no other 
green organism, by adding to it 4 to 1 its volume of alcohol. A 
greenish flocculent precipitate which slowly settles is formed, 
leaving a clear supernatant fluid which can be siphoned off. On 
warming the residue with aleohol a green extract is obtained, 
and on adding benzine the latter becomes dark green and shows 
the reddish fluorescence and the marked absorption-band in the 
red characteristic of chlorophyll. The fluid beneath is yellowish 
and may have a slight reddish tinge. Hence a trace of carotm 
may be present. If the green bacterial mass is treated with 
very dilute alkali and then ether is added, the latter acquires * 
U"-"— « 
