The Glow- Worm 



beside it is a curious air-tube, whose short 

 and remarkably wide stem branches suddenly 

 into a sort of bushy tuft of very delicate rami- 

 fications. These creep over the luminous 

 sheet, or even dip into it. That is all. 



The luminescence, therefore, is controlled 

 by the respiratory organs and the work pro- 

 duced is an oxidization. The white sheet 

 supplies the oxidizable matter and the thick 

 air-tube spreading into a tufty bush dis- 

 tributes the flow of air over it. There re- 

 mains the question of the substance whereof 

 this sheet is formed. The first suggestion 

 was phosphorus, in the chemist's sense of the 

 word. The Glow-worm has been calcined 

 and treated with the violent reagents that 

 bring the simple substances to light; but no 

 one, so far as I know, has obtained a satis- 

 facory answer along these lines. Phos- 

 phorus seems to play no part here, in spite of 

 the name of phosphorescence which is some- 

 times bestowed upon the Glow-worm's gleam. 

 The answer lies elsewhere, no one knows 

 where. 



We are better informed as regards an- 

 other question. Has the Glow-worm a free 

 control of the light which he emits? Can 

 he turn it on or down or put it out as he 

 pleases? Has he an opaque screen which 

 J9 



