366 PHILOSOPHY OF ZOOLOGY. 
Gulf of Guinea, the luminous property resided in the brain ; 
which, when the animal was at rest, resembled a most bril- 
lant amethyst, about the size of a large pin-head ; and from 
this there darted, when the animal moved, flashes of a bril- 
hant silvery light. In the Lampyris, the luminous matter 
is a soft yellowish substance, of a close texture, and re- 
sembling paste. It is not attached to the same part of the 
body, even in animals of the same class: thus, in the Lam- 
pyris, it is spread on the internal surface of the last rings 
of the abdomen. In the Elater, under the skin of the tho- 
rax ; in the Fulgora, in the remarkable projections on the 
head ; and in the Pausus, in the club of antenne*. 
Among insects, this luminous quality is peculiar to the 
season of love, and disappears during the remaining part of 
the year. The effect of season on the other luminous ani- 
mals, has not been observed. 
In many of the medusz, particularly Medusa hemisphe- 
rica of MaccarTNEy +, exposure to light destroys the lu- 
minous power ; hence these animals are not observed at the 
surface of the sea in moonlight nights. The light of in- 
sects appears to be in a great measure independent of ex- 
ternal circumstances. In the Scolopendra, on the other 
hand, the luminousness does not appear, unless the animal 
has been previously exposed to solar light. 
The luminous quality is not destroyed, extinguished, or 
altered, by immersing the animal in oxygen gas, chlorine, 
hydrogen, alcohol, or water, unless death be produced, in 
which case, the luminous power speedily ceases. In some 
cases, however, this power may be restored. Thus Mr 
Maccartney, to whom the public is indebted for the most 
valuable information on the subject which has yet been 

* Pausus spherocerus, Lin. Trans, vol, iv. p. 261. 
+ Phil. Trans. 1810, p. 268. 
