170 PHOSPHORESCENCE. LiECT. VIII. 



of certain substances on phosphorescence is proved, though 

 it is probable that they do not act by altering the phospho- 

 rescent matter. 



I tried the effect of varnishing the abdomen only, of a 

 great number of glow-worms with turpentine. I found 

 that the light became weaker, and the scintillations fewer, 

 but they did not entirely disappear. 



Microscopic Structure of the Luminous Organ. I ex- 

 amined the structure of the luminous organ by means of the 

 microscope. On the removal of the luminous segments of 

 the dorsal and abdominal membranes, there was perceived 

 a yellowish, granular, globuliform matter, in which appeared 

 groups of red globules, a great number of ramifications, and, 

 moreover, a species of tubes which had the appearance of 

 muscular fibre, but which, when closely examined, appeared 

 hollow. 



By looking at them at night, the light was seen to be 

 emitted by the granular yellow matter ; and when we com- 

 pressed this between two glasses, the light was always 

 observed on the edges of the examined portion. The ab- 

 dominal membrane examined alone, after it has been 

 washed several times in water in order to remove from it 

 all the phosphorescent matter, is transparent, and furnished 

 with a great number of hairs. The dorsal membrane, less 

 transparent than the former, is likewise hairy, but it is also 

 supplied, on its internal surface, with many tubes or trachea?, 

 which penetrate the phosphorescent matter. I must further 

 add, that I never separated the abdomen of a glow-worm 

 without finding under the last luminous ring but one, a 

 bright red vesicle, which, viewed by the microscope, is 

 found to be made up of a group of red globules. I have 

 never met with this vesicle in other insects of the same 

 genus, and no work on comparative anatomy mentions it. 



