THE GLOW-WORM 



result : the illumination continues, as bright and placid 

 as before. I take a spray, and rain down a slight shower 

 of cold water upon the flock. Not one of my animals 

 puts out its light; at the very most there is a brief pause 

 m 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 lamps 

 put out, but they are soon relit. Calm returns, and the 

 light is as bright as ever. I take some of the captives 

 in my fingers and tease them a little. Yet the illumina- 

 tion is not much dimmed, if I do not press too hard with 

 my thumb. Nothing short of very serious reasons would 

 make the insect 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 

 circumstance over which the insect has no control. If 

 I cut off a strip of the skin, showing one of the luminous 

 belts, and place it in a glass tube, it will shine away 

 merrily, though not quite as brilliantly as on the living 

 body. The presence of life is unnecessary, because the 

 luminous skin is in direct contact with the air, and the 

 flow of oxygen through the air-tube is therefore not re- 

 quired. In aerated water the skin shines as brightly as 

 in the free air, but the light is extinguished in water that 

 has been deprived of its air by boiling. There could be 



[67] 



