OXYGEN FROM COLOURED BACTERIA. 151 
given. S. varians, in addition to the characters above described, 
forms thiek-walled, colourless arthrospores, sometimes laterally, 
but generally intercalary to the chains, occasionally a pair being 
formed together. 
Attempts were made to obtain direct analytical proof of the 
presence of the power of assimilation in these green Bacteria by 
enclosing a given quantity of an almost pure green water-culture 
in glass tubes with a given volume of gas to light, andin darkness, 
for 12 hours, then opening and analysing the enclosed gas. 
It appears, therefore, as if under the most favourable conditions 
and using an atmosphere of hydrogen a trace of oxygen may 
Amount a. 
of fluid. Condition. Gas enclosed. Exposure. Da "" 
p. e. 
90 c.c. | Living. 17-10. | Bright diffuse | 5. :3 p. 
iving 15 c.e. l 14360, daylight, 29 Pe |93 p.e 
50 c.e. ” D» Darkness. 49 , |85 ,, 
Bee) y Tec. H. 7 85 , |00 , 
» Killed by HgCl,. » Light. 0:3 » 0:0 » 
” Living. ” ” 1:03 ” 0:0 » 
” » "n » 0:36 » 00 ,, 
Thick dark green 
” { almost pure culture, ] » » 46 n 0:37 ,, 
” ” ” m 3:9 » 10-79 ” 
” | 
” » Darkness. 92 „ |00 , 
| 
he ni In all cases, in light less CO, is evolved and less oxygen 
du. i ed tham in darkness ; but this might be explained as being 
instead ‘thas, action of light upon the respiration of the Bacteria, 
taken plac E due to a certain amount of assimilation having 
Certain and he analytieal results do not, therefore, form a 
sure proof of the presence of assimilation. It is 
Ossi : 
à "s however, that with perfectly pure cultures more certain 
esults may be obtaine d. 
Purple Bacteria. 
ascribes to these the power of assimilation, the 
ment being bacterio-purpurin. One peculiarity 
* TW 1s that it has a marked absorption-band in the 
Engelmann “Di > . . 
icht,” i , S j zum 
Licht, in Bot, Zeit. Oct, m Purpurbakterien und ihre Beziehungen 
Engelmann * 
évimilatory pig 
of this pigment 
