NATURAL HISTORY. 



G43 



the light, and never could serve 

 to extinguish it. The regulation 

 of the kind and degree of the lu- 

 minous appearance does not de- 

 pend upon any visible mechanism, 

 but, hke the production of the 

 light itself, is accomplished by 

 some inscrutable change in the lu- 

 minous matter, which in some 

 animals is a simple operation of 

 organic life, and in others is sub- 

 ject to the will. 



It is worthy of remark, that in 

 all the dissections I have made of 

 luminous insects, I did not find 

 that the organs of light were bet- 

 ter or diflPerently supplied with 

 either nerves or air tubes than the 

 other parts of the body. The 

 power of emitting light likewise 

 exists in many creatures which 

 want nerves ; a circumstance 

 strongly marking a difference be- 

 tween animal light and animal 

 electricity. 



With the exception of the ani- 

 mals above mentioned, the exhibi- 

 tion of light depends upon the 

 presence of a fluid matter. 



In the phoias dactylus, the lu- 

 minous fluid is particularly evi- 

 dent, and in vast quantity ; it is 

 recorded by Pliny, that this fluid 

 is like liquid phosphorus, and 

 renders every object luminous with 

 which it comes into contact. 

 Keaumur also found that it was 

 diffusible in water, or any other 

 fluid in which the animal might 

 be immersed. 



The shining of the scolopendra 

 electrica I have always observed to 

 be accompanied by the appear- 

 ance of an effusion of a luminous 

 fluid upon the surface of the ani- 

 mal, more particularly about the 

 head, which may be received 

 upon the hand, or other bodies 



brought into contact with the in- 

 sect at the moment, and these ex- 

 hibit a phosphoric light for a few 

 seconds afterwards. This fluid, 

 however, I never could discover 

 in the form of moisture, even upon 

 the clearest glass, although exa- 

 mined immediately with the most 

 scrupulous attention by a lens : it 

 must therefore be extremely 

 attenuated. 



The same appearance has been 

 observed during the illumination 

 of the nereis noctiiuca by Fouge- 

 roux de Bondaroy, 



The animal discovered by Ri- 

 ville shed a blue liquor, which il- 

 luminated the water for a distance 

 of two or three lines. 



Spallanzani relates, that the 

 medusa which he examined com- 

 municated the property of shining 

 to water, milk, and other fluids, 

 on being rubbed or squeezed in 

 them. 



The luminous fluid is in some 

 instances confined to particular 

 parts of the body, and in others 

 is diffused throughout the whole 

 substance of the animal. 



In the scolopendra electrica, it 

 appears to reside immediately un- 

 der the integuments. In the lyn- 

 ceus discovered by Riville, it is 

 contained in the ovary. If I may 

 judge from my own observations, 

 every part of the body of the me- 

 dusae is furnished with this fluid, 

 as there is no part I have not seen 

 illuminated under diflerent cir- 

 cumstances ; but Spallanzani af- 

 firms that it is only found in the 

 large tentacula, the edges of the 

 umbella, and the purse, or central 

 mass; which he proved, he says, 

 by detaching these parts succes- 

 sively, when they shone vividly, 

 while the rest of the body neither 



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