¥811.] 
‘Juminous spots in the water, and when 
the animals, supposed to be the cause of 
them, were examined, they were found 
to be insects about the third of an inch 
in length, resembling in appearance the 
weod-louse. The insect, when viewed 
with the microscope, seemed to be 
formed by-sections of a thin crustaceous 
substance. During the time that any 
fluid remained’ in the animal, it shone 
brilliantly like the fire-fly. Mr. Mac- 
artney supposes that this, and another 
Mentioned as taken on a sandy beach, 
were monoculi. He notices many others 
that have from time to time come under 
his inspection ; one of these, which he de- 
nominatesthe berve fulyens, is avery ele- 
gant creature, changing its colour be- 
tween purple, violet, and pale blue: the 
body is truncated before and pointed 
~behind,, but the exact form is difficult to 
assign, as itis varied by particular con- 
tractions, at the animal’s pleasure. When 
this insect swam gently neat the surface 
of the water, its. whole body became oc- 
casionally illuminated in a slight degree: 
daring its contractions, a stronger light 
issued from the ribs, and when a sudden 
shock was communicated to the water, 
in which several of these animals ‘were 
placed, a vivid flash was thrown out. 
If the body were broken, the fragments 
continued luminous for several seconds, 
and ‘being rubbed on the hand, left a 
light like that of phosphorus; this, how- 
ever, as well as every other mode of 
emitting light, ceased after the death of 
the animal. Mr. Macartney having 
noticed many other species, says, that his 
own observations lead him to conclude, 
that the medusa scintillans is the most 
frequent source of light of the sea round 
this country, and likewise in other parts 
of the world. We are next informed, 
that the remarkable property of émitting 
light during life, is only met with among 
animals of the four last classes of modern 
naturalists, viz. mollusca, insects, worms, 
and zoophytes. The mollusca and 
worms contain each but a single species ; 
the pholas dactylus in the one, and the 
Nereis nocticula in the other, - Some 
species yield light in the eight following 
genera of insects, viz. elater, lampyris, 
fulgora, pausus, scolopendra, cancer, 
lynceus, and limulus. The luminous 
“species of the genera lampyris and ful- 
ora, are more numerous than is gene- 
rally supposed. Among the zoophytes, 
the genera medusa, beroe, and penna- 
tula, contain species which afford light. 
The only animals that appear to possess 
"© Montury Mac, No, 211, 
Proceedings of Learned Societies, 
v4 
257 
a distinct organization for the production 
of light, are the Juminous species of lam. 
yris, elater, fulgora, and pausus. 
“The light of the lampyrides proceeds 
from some of the last rings of, the ab- 
domen, which, when not illuminated, 
are o! a yellowcolour, The number of 
luminous rings varies in different species, 
and, as it seems, at different periods in 
the same individual. Besides this lu-" 
minous substance there are, in the com- 
mon glow-worm, on the inner side of the 
last abdominal ring, two bodies, which to 
the naked eye appear more minute than 
the head of the smallest pin. | They are 
lodged in two slight depressions, formed 
in the shell of the ring, which is at these 
points, particularly transparent. These, 
when examined, were found to be sacs, 
and contain a soft yellow substance. 
The light that. proceeds from these sacs 
is less under the controul of the ansect 
than that of the luminous substance 
spread on the rings: it is seldom ene 
tirely extinguished in the season that 
the glow-worm gives light, even during 
the day; and when all the other rings 
are dark, these sacs often shine brightly, 
In all the dissections made. by Mr. Mac- 
artney, of luminous insects, he did not 
find that the organs of light were better, 
or differently supplied with either nerves 
or air-tubes, than other parts of the 
body. ‘The power of emitting light like- 
wise exists in some creatures which want 
nerves; a circimstance that strongly 
marks the difference between animal 
light and animal electricity. In ge- 
neral, the exhibition of light, in animals, 
depends upon the presence of a fluid 
matter, which in some instances 1s con= 
fined to particular parts of the body, and 
in others is diffused throughout the whole 
substance of the animal. 
Mr. Macartney next notices the vas 
rious explanations that have been given 
of the phenomena of animal light, and 
relates a number of experiments on the 
subject; and then gives the following 
conclusions, which are the result of the 
observations that he has made on the 
subject. ; 
‘The property of emitting hight is cone 
fined to animals of the simplest organi- 
zation, the greater number of which are 
inhabitants of the sea.) The luminous 
property is not constant, but in - general 
exists only in certain periods~in parti- 
cular states of the animal body. The 
power of shewing light resides in a par- 
ticular substance, or fluid, which is somes 
times situated in a particular organ, and 
ek ia 
