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The entire phenomena of the exhibition of light in 

 luminous terrestrial animals seems to us to hinge oh 

 a thermo-electric principle. We have clearly proved 

 experimentally, that the light varies in intensity with 

 specific temperatures, and the variations of tempe- 

 rature connected with a languid or accelerated cir- 

 culation will account satisfactorily for the change of 

 intensity in the light. That in the ova, in all pro- 

 bability, depends on the* vitality of its punctum sa- 

 liens ; and while we have observed, constantly, the 

 intermission in its intensity in the living glow-worm, 

 which has been ascertained by Dr. Carus to have 

 a correspondence with the circulation, we never 

 observed any such varying intensity in the ova pro- 

 truded from the insect, or the luminous matter insu- 

 lated from the body of the animal ; circumstances 

 which seem to corroborate the view we have taken 

 of it. Various have been the opinions hazarded on 

 the part to which this singular phenomenon is subserv- 

 ient in the animal economy: in the common glow- 

 worm it has been supposed to be a hymeneal torch, 

 like the lamp that lighted Leander to Hero's bower. 

 To this opinion many objections may be opposed. 

 The male as well as the female glow-worms are lumi- 

 nous ; the one is winged and the other apterous : the 

 light is visible in autumn as well as in summer, when 

 it cannot be required : the scolopendra electrica, which 

 crawls on the earth, as well as the elater, fulgora, 

 &c. which soar in the air, are luminous in both sexes. 

 In fact, we are inclined to think it is a land' of ignis 

 fatuus, by which its prey is more readily secured, just 

 as the moth or the gnat, attracted by the flame of the 

 taper, rushes on self-destruction. The employment at 

 the moment, of its palpi, seems to corroborate the 

 conclusion. This seems in our opinion to be its chief 

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