316 
POPULAR SCIENCE REVIEW. 
number of organs. Ray first noticed the light-organs of the 
male. Geoffry counted four such. Muller saw only two shining. 
It appears that Lamp, splend. has four, and Lamp. noct. two y 
according to Kolliker. Lampyris splend. is often found in 
Germany, but rare in England. The Italian Lampyris is a 
much more brilliant insect. In Russia a species named Corusca 
is found. In America an extraordinary number of species are 
known. 
Anatomy. — All the fight-organs have the same structure, 
being composed of an envelope (capsule), a parenchyma of 
cells, and a minutely ramifying system of tracheae. Fine 
nerves are also found imbedded in the cellular parenchyma ; 
the nerves are recognized with difficulty, being very pale, and 
without neurilemma ; they enter with the tracl^ae, but are soon 
lost in the interior of the organ ; the nerve substance appears 
slightly enlarged at the points of bifurcation, where from two 
to five twigs are given off ; the nerve fibrils have not been 
traced to their termination, nor any continuation with the cells 
demonstrated. The mass of the organ consists of cells which 
are of two kinds. In one kind the cells are pale, but contain 
minute granules, amidst which a distinct nucleus may be recog- 
nized. In the other kind the cell contents are granular, and 
appear under the microscope so stuffed with refractive granules, 
that no other elements can be made out. The pale clear cells 
fie chiefly next to the surface of the skin in Lamp, splendidula 
(both male and female), and in female noctiluca; the fatty 
white-looking cells fill up the deeper portion of the organ, and 
also the superficial portion of the small lateral organs of male 
Lamp, noctiluca and female splendidula. The essential illumi- 
nating substance does not consist of the granular matter of 
the white cells, but of the clear pale cells, the chemical reac- 
tion of whose contents is that of albumen. The granular par- 
ticles of the white cells are composed of urate of ammonia. No 
phosphorus could be found, though perseveringly sought for. 
Physiology . — The emission of light occurs by day as well as 
by night, but chiefly at night, when the insect is naturally 
more active. It appears to be under the insect* s control, but 
does not depend on muscular action, which may be very active 
without emission of fight ; nor does exposure to fight influence 
the activity of functions even after the insect has been kept in 
the dark for days together. The production of fight is excited 
by mechanical injury, by application of the induction spark, by 
increased temperature, by various re-agents, e.g., alkalies, mi- 
neral and vegetable acids ; solutions of sugar, salt, and neutral 
salts ; by dilute alcohol, ether, chloroform, chlorine vapour, and 
creosote. Without effect are water, saliva, oil, hydrocarbons, 
dilute salts and acids, and metal salts. 
