ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
81 
with Bacterium phosphor escens, finds that on salt-gelatin stained red with 
phloxin, the bacteria grew up of a red colour, and on methylen-blue- 
gelatin a dark blue. The coloration was intimately associated with the 
presence of oxygen, for along the needle track the bacteria were 
colourless. 
The appearance of the organisms under the Microscope was very 
variable. In young colonies the most frequent forfli was short rods with 
rounded ends. These were usually in pairs. As the colony grew older, 
the rodlets tended to become ovalish or spheroidal, and were mixed up 
with all kinds of involution-forms. No spores were observed, and 
specific movements were quite absent. 
If the gelatin were only slightly acidulated (acetic acid), the fungus 
grew brilliantly, but increased acidulation diminished development, and 
finally stopped it. Similar observations were made with alkalies. 
The illuminating power of these bacteria seems to depend entirely on 
the presence of oxygen. On saline media a green-coloured light is 
developed ; while, if the salinity be scanty, the light is less and more 
yellowish. The light is developed only on the surface of the culture, 
the organisms in the deeper parts being non-illuminant. Hydrogen, 
carbonic acid, and carbonic oxide rapidly extinguish the light. If a 
liquid medium be shaken up, the whole fluid becomes phosphorescent. 
The fungus was found not only to be able to live well but to grow 
without developing light. 
The phosphorescence originates in one of two ways : — (1) The process 
is intracellular ; that is, the molecular processes within the cells, which 
in general give rise to heat, the formation of carbonic acid, &c., are here 
followed by the development of light ; or (2) the bacteria produce 
by their metabolism a substance which unites with oxygen outside the 
cells, and thereby light is produced. The formation of such a photogenic 
substance would place it on a level with the chromogenous substances 
produced by some bacteria, e. g. by Bacillus prodicjiosus. 
The fact that the light is wanting after filtrations through porcelain, 
and disappears on the addition of disinfectants, would seem to favour 
the extracellular theory. But experiments at different temperatures de- 
cided the author in favour of the intracellular view. It was found that 
the greatest light was given off at 24° 0., and that it was extinguished at 
39 • 5°. On cooling the culture down to 0*1°, a faint light was observed 
for four days, and even at — 12° the light remained for 10-12 minutes. 
Certain gases, such as CO, COg, and H, were found to extinguish by 
merely preventing the access of oxygen ; while H^S acted toxically, the 
illumination rapidly disappearing and not returning on the cultivation 
being shaken up with air, while after-inoculations showed that it was 
sterilized. Sulphate of morphia produced no efiect, nor did saponin. 
Strychnine had a slow and slight influence on the phosphorescence ; 
while sulphate of quinine had a decided result. 
Photobacterium luminosum.* — M. W. Beyerinck describes a new 
phosphorescent bacterium which he obtained from the sea water near 
Scheveningen. 
The edge of puddles left by the retreating tide on a warm summer’s 
* Arch. Nccrland. Sci. Exact, ct Nat., xxiii. (1889) pp. 101-5 (1 figs.). 
1890. G 
