648 



ANNUAL REGISTER, 1810. 



without any other food than what 

 a small quantity of filtered sea- 

 water would afford. The unin- 

 terrupted and long continued light 

 that is sometimes evolved by the 

 luminous sacs, and the ova of the 

 glow-worm, is also inconsistent 

 with the notion of an accumula- 

 tion and subsequent dispersion of 

 a material substance. 



I shall terminate this paper by 

 an enumeration of the several 

 conclusions, that arc the result of 

 the observations I have been able 

 to make upon the phsenomena of 

 animal light. 



The property of emitting light 

 is confined to animals of the sim- 

 plest organization, the greater 

 number of which are inhabitants 

 of the sea. — The luminous pro- 

 perty is not constant, but in ge- 

 neral exists only at certain pe- 

 riods, and in particular states of 

 the animal's body. — The power 

 of shewing light resides in a pe- 

 culiar substance or fluid, which 

 is sometimes situated in a particu- 

 lar organ, and at others diffused 



throughout the animal's body. 



The light is differently 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 alter- 

 nated with periods of darkness ; 

 is commonly produced or increas- 

 ed by a muscular effort ; and is 

 sometimes absolutely dependent 

 upon the will of the animal. In 

 the second case, the luminous 

 appearance is usually permanent 

 until it becomes extinct, after 

 which it may be restored directly 

 by friction, concussion, and the 

 application of warmth ; which last 

 causes operate on the luminous 



matter (while in the living body,) 

 only indirectly by exciting the 

 animal. — The luminous matter, in 

 all situations, so far from posses- 

 ing phosphoric properties, is in- 

 combustible, and loses the qua- 

 lity of emitting light, by being 

 dried, or much heated. — The ex- 

 hibition of light however long it 

 may be continued, causes no di- 

 minution of the bulk of the lu- 

 minous matter. It does not re- 

 quire the presence of pure air, 

 and is not extinguished by other 

 gases. 



The luminous appearance of 

 living animals is not exhausted 

 by long continuance, or frequent 

 repetitions, nor accumulated by 

 exposure to natural light ; it is 

 therefore 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 all the other functions of 

 living beings. 



The light of the sea is always 

 produced by living animals, and 

 most frequently by the presence 

 of the medusa scintillans. When 

 great numbers of this species ap- 

 proach the surface, they some- 

 times coalesce together, and cause 

 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 light, somewhat like an elec- 

 tric coruscation. When the lu- 

 minous medusae are very nume- 

 rous, as frequently happens in 

 confined bays, they form a con- 

 siderable portion of the mass of 

 the sea, at which times they 

 reader the water heavier, and 



