LUMINOUS INSECTS. 421 



tapers a , is incapable of inflammation if applied to the 

 flame of a candle or red-hot iron ; and when separated 

 from the body exhibits no sensible heat on the thermo- 

 meter's being applied to it rejects the preceding hypo- 

 theses as unsatisfactory, but without substituting any 

 other explanation; suggesting, however, that the facts 

 he observed are more favourable to the supposition of 

 light being a quality of matter than a substance b . 



Which of these opinions is the more correct I do not 

 pretend to decide. But though the experiments of Mr. 

 Macartney seem fairly to bear him out in denying the 

 existence of any ordinary combination of phosphorus in 

 luminous insects, there exists a contradiction in many of 

 the statements, which requires reconciling before final 

 decision can be pronounced. The different results ob- 

 tained by Forster and Spallanzani, who assert that glow- 

 worms shine more brilliantly in oxygene gas, and by 



a " And for night-tapers crop their waxen thighs, 

 And light them at the fiery glow-worms' eyes." 



b Some experiments made by my friend the Rev. R. Sheppard on 

 the glow-worm are worthy of being recorded. One of the recepta- 

 cles being extracted with a penknife, continued luminous ; but on 

 being immersed in camphorated spirit of wine, became immediately 

 extinct. The animal, with one of its receptacles uninjured, being 

 plunged into the same spirit, became apparently lifeless in less than 

 a minute j but the receptacle continued luminous for five minutes, 

 the light gradually disappearing. Having extracted the luminous 

 matter from the receptacles, in two days they were healed, and filled 

 with luminous matter us before. He found this matter to lose its 

 luminous property, and become dry and glossy like gum, in about 

 two minutes ; but it recovered it again on being moistened with 

 saliva, and again lost it when dried. When the matter was extracted 

 from two or three glow-worms, and covered with liquid gum-arabic, 

 it continued luminous for upwards of a quarter of an hour. 



