\ 
102 Observations upon Luminous Animals. 
T may further add, thac Spallanzani’s experiments of 
diffusing the lomious liquor of the medusa in water, milk, 
and other flui: ils, are in direct contradiction of his own 
theory, as is mje the extinction of the light of these mix- 
tures by the application of ahigh 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 3 
but we do not find this to be the case; for in those gitua- 
tions 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 Jiving animals are 
not only independent of all foreign light, but are frequently 
destroyed by the latter. - I have ‘alw avs found the shining 
of the medusz to cease upon ‘the rising of the moon, or at 
the approach of day ; and when out of the sea, I never could 
excite them to elena out lieht until they had been kept for 
some time in the dark; all the luminous insects likewise 
secrete themselves as much as possible during the day time, 
and go abroad only at night. | 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 situation, as when left uncovered the 
whole day. The circumstance of the scolopendra requiring 
exposure previous to its giving out light, is very unaccounta-~ 
ble, as the insect, when left to itself, always seeks as much 
as possible concealment during the day; indeed it is the 
opinion of some naturalists that it is killed by the light of 
the sun. 
The opinions of Brugnatelli and Carradori are connected 
with some general doctrines, respecting the nature of light, 
which T shall not at present venture to discuss. . It appears 
to me, that the question is still unresolved, whether light 
has a substantial existence, or is a pheeriomenan depending 
upon certain operations or conditions of the ordinary forms 
of matter. But the highly ingenious researches of Count 
Rumford, on the laws of what have been called subtile fluids, 
and the extraordinary advances lately made by Mr. Davy, 
on the decomposition of substances that were hitherto 
Jooked upon as elementary, give us reason to hope, that 
future investigatious may unfold views of the material world, 
of which we can at present have only an indistinct concep- 
tion; that new modes of analysis may enable us to see 
things, 
