BASIS OF ANIMAL PHOSPHORESCENCE. 105 



was larger than the ordinary species, and had more divisions. 

 The power of emitting light in the ordinary worm seemed 

 proportionate to the age of the animal." 



Monday, Ht/i. " The matter of the worms referred to yes- 

 terday still shines. It was detached from the animal at 8.24, 

 and still promises to emit light much longer." 



Tuesday, I2th. "The matter was luminous this day at 

 10.41, though faintly, and at twelve o'clock no light could 

 be perceived. The matter had become quite dry and semi- 

 transparent, but the addition of water produced no particular 

 effect." 



Faraday's results may be briefly stated as follows : 



(1) There is a chemical substance in the glow-worm and the 

 fire-fly which has power to shine independently of the life of 

 the insect. 



(2) This substance is probably a secretion of the insect. 



(3) The shining depends on the respiration, and the air is 

 enough to cause this substance to shine. 



(4) From the variation in the splendor of light, accompanied 

 by motions in the living animal, the animal, as a whole, has 

 in some way the control of the external manifestation of light. 



Matteucci, also, in his letter to Duma, 1 and elsewhere, 2 came 

 to the same conclusion as Faraday, and says : " In the glow- 

 worm there is a substance which, without any sensible heat, 

 diffuses a light that does not require the integrity of the 

 animal and of its living state in order to manifest itself with 

 its peculiar properties." 



It will contribute to the clearness of the whole, if, instead of 

 examining various other theories proposed from time to time, 

 in the nature of animal light, I dwell briefly here on the rela- 

 tion of objective and subjective aspects of what we call the 

 sensation of light and of heat, or the relation of various kinds 

 of ether vibrations to the specific energy of senses. 



We habitually associate the sensation of light with that of 

 heat, so that it becomes almost impossible to separate them in 



1 Carlo Matteucci: Sur la phosphorescence du Lampyre d'ltalie (L. Italica). 

 Compt. Rend. XVII, p. 309, August 14, 1843. 



2 Matteucci : Lectures on the Physical Phenomena of Living Beings, 1848, p. 165. 



