284 THE WONDERS OF INSTINCT 



point at which the voluntary agency of the insect is 

 without effect. I detach a strip of the epidermis show- 

 ing 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 sub- 

 stance, 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 splendor, 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 touch- 

 ing one another. Each of them sheds its glimmer, which 

 ought, one would think, to light up its neighbors by 



