82 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
day is found to be passing ricli in bacteria. Some of such water is 
sown on the following media : — A decoction of fish is made in sea water, 
and to this 0*5 per cent, peptone and 7 per cent, gelatin are added. 
Some of the luminous puddle-sand is then mixed up with boiled sea 
water and a few lines traced across the gelatin with a needle dipped in 
the mixture. The gelatin is then covered with sea water, and the 
latter drained off. At the end of about twenty-four hours, at summer 
heat, numerous brightly luminous colonies will have appeared. P. lumi- 
nosum liquefies gelatin if this be efiected in the presence of a large 
quantity of nitrogenous matter. No foetid products are evolved, but 
when the amount of azotized material is insufficient, a putrefactive 
process takes place. Like other phosphorescent bacteria, P. luminosum 
developes only in neutral or slightly alkaline media, a small quantity of 
acid being sufficient to prevent 'the production of light. On gelatin or 
peptonized meat-broth the bacterium will not develope unless 3-3*5 per 
cent, of sea salt, of chloride of potassium, or chloride of magnesium be 
added. 
In form this bacterium varies with the cultivation medium. When 
this contains little nitrogen or a small quantity of carbohydrates, the 
bacterium is small, and resembles the cholera vibrio. Among the rods, 
spirilla, more or less long, may be seen, and these sometimes break up 
into short vibrios. Both spirilla and vibrios move rapidly towards the 
margins of the preparation, where they gain access to free oxygen, 
without which their development is impossible. 
Like other phosphorescent bacteria, descendant colonies of P. lumi- 
nosum frequently diminish in luminosity, and even cease to emit light. 
The exact conditions which give rise to this degeneration are not at 
present understood, but certain differences in the nutrient media have 
direct influence on the light-production. This diminution in the lumi- 
nosity is always accompanied by a similar diminution in the liquefying 
power, and also by changes in the shape of the organism. Among the 
substances which cause this diminution are glucose, levulose, maltose, 
and asparagin. 
Luminosity of Bacteria and its relation to Oxygen.* — In examining 
the relations between the luminosity of bacteria and free oxygen, M. W. 
Beyerinck employed three species of jffiotobacteria — P. phospliorescens, 
indicum, and luminosum. In addition to the physiological combustion 
from the influence of free oxygen to which the phosphorescence is owing, 
the reducing and fermenting functions had also to be taken into con- 
sideration. In estimating the amount of action excited by oxygen, the 
author made use of hydrosulphate of soda and indigo. His conclusions 
on the subject of luminous bacteria in general, and P. phosphor escens in 
particular, are that oxygen necessary for anaerobiosis, called fixed or 
exciting oxygen, is not of itself able to maintain phosphorescence, but 
it can keep up, at least to a certain degree, both the fermentative and 
reducing functions of the organism. 
As regards phosphorescence, the oxygen must be in a more free 
condition ; and though this oxygen is not physically dissolved in the 
Arch. Nccrlaiid, Sci. Exact, et Nat,, xxiii. (1889) pp. 416-27. 
