therefcr, depends upon thè will cf thè in« 
sect, If' One compresses thè ahdomen light- 
ly between thè thum and forfinger, in thè 
dark, there will follow, after ahout ten 
miriuts during which thè insect remains en- 
tirely dark, thè erniosi on cf light from thè 
next to thè last segment, which hy night 
rnay he clearly distinguisht from thè others, 
and thè light Ì3 of a pale azure color. 
Socn afterv\^ard they darken themselvs, and 
thè alternations of light and darkness he- 
come quite irregular in tirne. 
I had therefor a rneans cf chtaining it, al- 
tho extremely truhlescme, and this consisted 
in opening with thè pcint cf thè sisscrs thè 
rings from ìthich thè light comes, and for- 
cing cut some of thè whi ti^hanimal suh^.nce 
which is there enciosed, a siriall part of 
which is lumiinous and persiste so for some 
time, al tho seprated from thè body. 
Sec« 116: Cné cf these luccioloni whic>i 
in thè air shone int errup tedly between my 
hands, I placed in a udiom.eter of air over 
water, when there followd a repetition of 
thè 1 aminosi ty; but all light was extin- 
guisht in nitrogeni it was reste rd on thè 
resti tution cf thè air. It was m.ade mor 
intens by thè presence cf oxygen. Two 
other gases, carbon dioxid and hydrogen, 
extinguisht thè light as did nitregen. 
fhe luminous pcrtions separated from thè 
insect by a knife, became dark when in con- 
tact vv'ith thè three gases l^itrogen, hydro- 
gen and carbon dioxid, introduced into thè 
udiometer seprately, but became very bril”» 
liant in oxygen. 
