81 PHOSPHORESCENCE. 
in some small degree. One of the commonly occurring varieties in 
Brazil is called Fungus igneus. Luminous Fungi are also found in 
Italy. It is affirmed that a supply of oxygen is necessary for the 
exhibition of Phosphorescence in the Fungi that shew it and that if 
the oxygen is extracted—presumably by placing them in vacuo— 
the Phosphorescence ceases. 
And now we come to Phosphorescence amongst living things, 
so small that Nocrinuca is quite a large organism by comparison. 
I speak of the luminous bacteria, or bacteria whose life history is 
associated with Phosphorescence. Many authorities are agreed that 
in not a few cases where the bodies of sea-fish exhibit Phosphores- 
cence, either in or out of the water, that the luminosity is due to 
the activity of a whole series of marine bacteria. The cause of the 
Phosphorescence is at present unknown, Some of the hypotheses 
that have been advanced in explanations are :— 
(ty That it is due to the oxidation of a body secreted by the 
bacterium, i.e. Phosphorus, Phosphoretted Hydrogen, etc. 
(2) That Phosphoresence occurs at the moment that peptones 
are being worked up into living proto-plasm (BEYERINCK.) 
Some of the favouring conditions are known to be :— 
(a) The presence of free oxygen. 
(b) A relatively low temperature. 
(c) A nutrient medium containing Sodium Chloride and pep- 
tones, but little or no Carbohydrate food. 
Several kinds of Phosphorescent Bacteria have been pure-culti- 
vated. Such an one is Photobacterium Phosphorescens: this and 
other luminous bacteria react in a very curious way towards Oarbo- 
hydrates, starch, sugars, ete., growing in presence of some of these 
substances without phosphorescing, whilst with others, they phos- 
phoresce markedly ; so that to a certain extent they can be used to 
test for the presence of certain substances—Maltose, Levulose, etc. 
It is not certain that the Phosphorescence of freshly captured 
and cut fish, dried and cured fish, e.g. Haddock, etc. is always due to 
luminous bacteria. The phenomenon may set in with such rapidity 
