Olservations upon Luminous Animals. 103 
things, not * through a glass darkly,’’ but more nearly as 
they are; and that the boundaries of physical aud metaphy- 
sical bcién ee: now so far-asunder, may be made to approach 
‘each other. 
In the present state of our knowledge, our business should 
be, to collect, arrange, and compare phenomena, rather 
than to speculate upon their nature. Nevertheless, I. can- 
not refrain from observing, that the circumstances attending 
the luminous appearance of living animals, are much more 
favourable to the supposition of light being a property than 
a substance. “The quantity of light emitted by an animal 
in acertain time, (admitting it to be matter) far exceeds 
that which could be possibly supplied by the sources from 
whence it is usually supposed to be derived. Thus the Iu- 
minous aj pearance of some meduse may be continued with 
the intermission of short intervals for an indefinite time, 
notwithstanding the creature be kept in darkness, and with- 
out any other food than what a small quantity of filtered 
Sea-water would afford. The uninterrupted and long con- 
tinued light that is sometimes evolved by the luminous sacs, 
and the ova of the glow- worm, is also inconsistent with 
the notion of an accumulation and subsequent dispersion of 
a material substance. 
I shall terminate this paper by an enumeration of the 
several conclusions, that are the result of the observations 
T have been able to make upon the phenomena of animal 
light. 
The property of emitting light is confined to animals of 
the simplest organization, the greater number of which are 
inhabitants of the sea.—The luminous property is not con-= 
stant, but in weneral exists only at certain periods, and in 
particular states of the animal’s body.—The power of show- 
ing light resides in a peculiar substance or fluid, which is 
sometimes situated in a particular organ, and at others dif- 
fused throughout the animal’s body. alp the lighti is differently 
- regulated, when the luminous matter exists in the living 
body, and when it is abstracted from it. Jn the first case, 
it is intermitting, or alternated with periods of darkness ; 
is commonly produced or increased by a muscular efforts 
and is sometimes absolutely dependent upon the will of the 
animal, In the second case, the luminous appearance is 
usually permanent until it becomes extinct, after which it 
may be restored directly by friction, concussion, and the 
application of warmth; which last causes operate on the 
luminous matter (while i in the living bedy,) only indirectly, 
by exciting the anima).—The luminous matter, in all situ- 
G4 ations, 
