upon 'Luminous Animals. 287 
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 brilliant in 
oxygene, or in oxygenated muriatic gas, than in common air ; 
and that it is not sensibly diminished in hydrogene gas. 
I may further add, that Spallanzani's experiments of 
diffusing the luminous liquor of the medusa in water, milk, 
and other fluids, are in direct contradiction of his own theory, 
as is also the extinction of the light of these mixtures by the 
application of a high degree of heat. 
If the light emitted by animals were derived from their 
food, or the air they respire, as supposed by Carradori, the 
phenomenon should be increased or diminished, according to 
the quantity of food or air, that the creatures consume ; but 
we do not find this to be the case ; for in those situations 
where they are sometimes found to be most luminous, they 
are deprived, in a great measure, of these assumed sources of 
their light. 
In fact, the luminous exhibitions of living animals are not 
only independent of all foreign light, but are frequently des- 
troyed by the latter. I have always found the shining of the 
medusae to cease upon the rising of the moon, or at the ap- 
proach of day ; and when out of the sea, I never could excite 
them to throw out light until they had been kept for some time 
in the dark ; all the luminous insects likewise secrete them- 
selves as much as possible during the day time, and go abroad 
only at night. I have, it is true, found that the scolopendra 
electrica will not shine unless it has been previously exposed 
to solar light ; but I have observed that it shone as brilliantly 
and as frequently, after being kept a short time in a light 
Pp § 
