Olservations upon Luminous Animals. 101 
introdaced -into the receiver of an air-pump, and the air 
being exhausted, they shone as usual when shaken ; if any 
. difference could be perceived,’ the light was more easily ex- 
“cited, and continued longer in vacuum. 
I wished next to try the influence of electricity on the 
luminous property of animals. 
Experiment 10.—A medysa hemispherica was placed in 
a small glass dish, containing a quantity of water merely 
sufficient to allow the animal to preserve its figure; being 
insulated, it was electrified, and sparks drawn from. it, 
-which had not the slightest effect ; the experiment was re- 
peated several times with different individuals, but without 
exciting the animals to throw out light. 
Experiment \1.— Some hemispherical meduse were 
placed im contact with the two ends of an interrupted chain, 
and slight electric shocks passed through them. During 
the very moment of their receiving the shock no light was 
visible, but immediately afterwards the medusze shone like 
illuminated wheels, which appearance remained for some 
seconds. Upon the closest inspection with a magnifying. 
glass, no contractile motion could be perceived to accom~ 
pany the exhibition of the light. The application of elec- 
tricity es ins ance seems to have acted merely as a 
strong méchanic s . 
rock. 
The above experiments on the luminous medause were 
made at Herne, with the »assistance of George May, Esq. 
of Stroud-house, and in the presence of a large company, 
capable of accurately distinguishing their results. 
It seems proved by the foregoing experiments, that so far 
from the luminous substance being of a phosphorescent na- 
ture, it sometimes shows the strongest and most constant 
light, when excluded from oxvgen gas; that it in no cir- 
cumstances undergoes any process like combustion, but is 
actually incapable of being inflamed; that the increase of 
heat, during the shining of glow-worms, is an accompani- 
ment, and not an effect of the phenomenon, and depends 
upon the excited state of the insect; aud lastly, that heat 
and electricity increase the exhibition of light, merely by 
operating like other stimuli upon the vital properties of the 
animal. 
In confirmation of these opinions, I may quote the high 
authority of the Secretary of this Society, who has found 
-that the light of the glow-worm is not rendered more bril- 
liant im oxygen, or in oxygenated muriatic gas, than in 
common air; and that it is not sensibly diminished in hy- 
drogen gas. 
: G3 I may 
