. VIII. PHOSPHORESCENT ANIMALCULES. 173 



this way we account for the effects produced by some agents 

 on the phosphorescent substance alone, when separated from 

 the animal. The example of an organic substance which 

 burns in the air by absorbing oxygen and emitting carbonic 

 acid, is not new ; this is the case with decaying wood, with 

 oiled cotton, with very finely divided charcoal, and many 

 other substances liable to spontaneous combustion. If, in 

 the case which now engrosses our attention, the heat which 

 ought to accompany the chemical combination be wanting, 

 it may be easily explained. The quantity of carbonic acid 

 disengaged from the luminous segments of each of these 

 insects in a given time, is so small that the heat developed 

 cannot accumulate there. The phosphorescence of wood, 

 to which I alluded just now, as well as many other cases 

 in which an emission of light accompanies chemical com- 

 binations, but which I need not farther notice, clearly prove 

 that a disengagement of light may take place without any 

 perceptible augmentation of temperature. Heat requires to 

 be accumulated in order that its presence may be discovered 

 by our instruments; and it is in this way we explain our 

 inability to detect heat in the animals termed cold- 

 blooded. 



I have thought it my duty to enter thus fully into the 

 peculiarities relative to the phosphorescence of the glow- 

 worm, because I intend only slightly to allude to other 

 cases of animal phosphorescence. 



Phosphorescent Animalcules. Every one knows, that 

 during the night there is observed in the sea vast luminous 

 tracts, which were formerly vaguely ascribed to the clash- 

 ing of waves, to electricity, or to phosphuretted gases 

 formed by the putrefaction of the mollusca. We now 

 believe them to be owing to an immense number of phos- 

 phorescent microscopic animalcules. But no. one knows 



