upon the flock. Not
one of my animals puts out its light; at the very most, there is a
brief pause in the radiance; and then only in some cases. I send a puff
of smoke from my pipe into the cage. This time the pause is more
marked. There are even some extinctions, but these do not last long.
Calm soon returns and the light is renewed as brightly as ever. I take
some of the captives in my fingers, turn and return them, tease them a
little. The illumination continues and is not much diminished, if I do
not press hard with my thumb. At this period, with the pairing close at
hand, the insect is in all the fervour of its passionate splendour, and
nothing short of very serious reasons would make it put out its signals
altogether.

All things considered, there is not a doubt but that the Glow-worm
himself manages his lighting apparatus, extinguishing and rekindling it
at will; but there is one point at which the voluntary agency of the
insect is without effect. I detach a strip of the epidermis showing one
of the luminescent sheets and place it in a glass tube, which I close
with a plug of damp wadding, to avoid an over-rapid evaporation. Well,
this scrap of carcass shines away merrily, although not quite as
brilliantly as on the living body.

Life's aid is now superfluous. The oxidizable substance, the
luminescent sheet, is in direct communication with the surrounding
atmosphere; the flow of oxygen through an air-tube is not necessary;
and the luminous emission continues to take place, in the same way as
when it is produced by the contact of the air with the real phosphorus
of the chemists. Let us add that, in aerated water, the luminousness
continues as brilliant as in the free air, but that it is extinguished
in water deprived of its air by boiling. No better proof could be found
of what I have already propounded, namely, that the Glow-worm's light
is the effect of a slow oxidation.

The light is white, calm and soft to the eyes and suggests a spark
dropped by the full moon. Despite its splendour, it is a very feeble
illuminant. If we move a Glow-worm along a line of print, in perfect
darkness, we can easily make out the letters, one by one, and even
words, when these are not too long; but nothing more is visible beyond
a narrow zone. A lantern of this kind soon tires the reader's patience.

Suppose a group of Glow-worms placed almost touching one another. Each
of them sheds its glimmer, which ought, one would think, to