156 PHOSPHORESCENCE. LiECT. VIII. 



ish matter. The phosphorescence continues for a greater 

 or less, period, according to a variety'bf circumstances, 

 which we shall presently investigate. Indeed, this fact 

 proves that the integrity and life of the animal are not es- 

 sentially necessary for its production. In order to study 

 the matter, thus separated from the body of the insect, I 

 commenced by examining what influence heat, electricity, 

 and gaseous media had on it, as those persons had done, 

 who preceded me in this curious inquiry. At the same 

 time, I also studied the influence of the same causes on an 

 entire and living insect ; and thus, by comparison, I believe 

 I have adopted the best method of ascertaining the nature 

 of the phenomenon. 



Effect of Heat on the Glow-worm. I placed several very 

 lively and very luminous glow-worms in a glass tube im- 

 mersed in water. A thermometer with a very small bulb 

 was surrounded by these insects. I have repeatedly endea- 

 voured to ascertain whether the thermometer thus placed 

 acquired, in consequence, a higher temperature, but have 

 never observed that it did. By slowly heating the water, I 

 saw the intensity of the light increase up to + 30 Reau- 

 mur. [ = 99-5 Fahr.] At about this temperature the in- 

 termittence ceased, the light became continuous, and, by 

 applying more heat, acquired a red colour. At -f 40 

 Reaumur [ = 122 Fahr.] the light entirely and finally 

 ceased, and the animal died. By crushing the matter from 

 the rings between the fingers, it no longer evolved light. 



In experimenting with the posterior luminous segments, 

 instead of entire glow-worms, I discovered no difference 

 in the phenomena. These results confirm the experiments 

 made by Macaire on entire glow-worms, placed in water 

 which was gradually heated. 



Effect of Cold. I found some differences between my 

 results and those obtained by this philosopher when the 



