THE GLOW-WORM 281 



The male, on his side, is fully transformed, changes 

 his shape, acquires wings and wing-cases; nevertheless, 

 like the female, he possesses, from the time when he is 

 hatched, the pale lamp of the end segment. This lumi- 

 nous aspect of the stern is characteristic of the entire 

 Glow-worm tribe, independently of sex and season. It 

 appears upon the budding grub and continues through- 

 out life unchanged. And we must not forget to add 

 that it is visible on the dorsal as well as on the ventral 

 surface, whereas the two large belts peculiar to the 

 female shine only under the abdomen. 



My hand is not so steady nor my sight so good as 

 once they were; but, as far as they allow me, I consult 

 anatomy for the structure of the luminous organs. I 

 take a scrap of the epidermis and manage to separate 

 pretty nearly half of one of the shining belts. I place 

 my preparation under the microscope. On the skin a 

 sort of white-wash lies spread, formed of a very fine, 

 granular substance. This is certainly the light-producing 

 matter. To examine this white layer more closely is 

 beyond the power of my weary eyes. Just beside it is 

 a curious air-tube, whose short and remarkably wide 

 stem branches suddenly into a sort of bushy tuft of very 

 delicate ramifications. 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 produced is an oxidiza- 

 tion. 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 remains the ques- 



