ON LUMINOUS ANIMALS. ^^ 



showing light resides in a peculiar substance or fluid^ which 

 is sometimes situate in » particular organ» and at others, 

 diffused throughout the ajiimars body. — ^The light is dif- 

 ferently regulated, when the luminous matter exists in the 

 living body, and when it is abstracted from it. In the first 

 case, it is intermitting, or alternated with periods of dark* 

 ness; is commonly produced or increased by a muscular 

 effort ; and is sometimes absolutely dependant upon the 

 will of the animal. In the second case, the luminous ap- 

 pearance is usually permanent until it becomes extinety 

 after which it may be restored directly by friction, concus* 

 sion, and the application of warmth; which last causes, 

 operate on the luminous matter (vvhile in the living body,) 

 only indirectly, by exciting the animal. — The lummouft 

 matter, in all situations, so far from possessing phosphoric 

 properties, is incombustible, and loses the quality of emit- 

 ting light, by being dried, or much heated. The exhibition 

 of light, however long it may be continued, causes no dimi- 

 nution of the bulk of the luminous matter. It does not 

 require the presence of pure air, and is not extinguished 

 by other gasses. 



The luminous appearance of living animals is not ex- 

 hausted by long continuance, or frequent repetitions, nor 

 a<*cnmulated by exposure to natural light; it is, theiefore, 

 not dependent upon any foreign source, but inheres as a 

 property, in a peculiarly organized animal substance or 

 fluid, and is regulated by the same laws, which govern alt 

 the other functions of living beings, ' • -> 



The light of the sea is always produced by living anl«Luminow$ness 

 mals, and most frequently by the presence of the medus^^^ '^*"*** 

 scintillans. When great numbers of this species approach 

 the surface, they sometimes coalesce together, and cd»i0" 

 that snowy or milky appearance of the sea, which is so 

 alarming to navigators. These animals, when congregated 

 on the surface of the water, can produce a flash of li<rht, 

 somewhat like an electric corruscation. When the lumi- 

 nous medusae are very numerous, as frequently happens in 

 confined bays, they form a considerable portion of tfie' 

 mais of the sea, at livhich times they render the water 



heavier 



