JURA. LUMINOUS ANIMALS. 197 



to be deduced from this phenomenon will not be mate- 

 rially affected ; as they will be the same whether the light 

 generated by the actions of the several tribes be internal 

 or external ; whether it be a property residing in the body 

 of the animal, or liable to be called into action from with- 

 out, by collision against the bodies of other animals, or 

 against the luminous mass of the sea. 



Although some labour has been exerted in attempting 

 to ascertain the nature of the phosphorescent power, or 

 the substance in which this property resides, no real 

 light has hitherto been thrown on the subject. It is 

 however known that it can exist independently of the 

 animal by which it is generated, that it continues at- 

 tached to the body after the principle of life has ceased, 

 that it can even be separated in a state of mixture or 

 combination with the mucous secretions, and that it is in 

 this state diffusible through the sea, communicating to it 

 the luminous property. Thus far then it is, in some cases, 

 independent both of the principle of life and of the action 

 of animal energy. We have therefore reason to conclude 

 that it is an animal secretion, and consequently a chemical 

 substance, of which the nature and properties are subject 

 to investigation. 



From these several facts it may be deduced, that the pro^ 

 perty of emitting light, so far from being confined to a few 

 species or genera, is widely diffused among the more 

 imperfect marine animals, and that it occurs even among 

 the higher orders of fishes. On our own shores, it appears 

 to reside in almost all the marine worms, and is, for 

 evident reasons, particularly conspicuous in those which 

 are produced in the greatest abundance and which swim 

 nearest to the surface. The Medusae therefore are, with 

 us, the glow worms of the deep ; emulating in dark nights, 

 by their brilliancy and intermitted sparklings, the more 

 distant lights that spangle the sky, and illuminating in 

 a sensible degree the darkness of the ocean. There 

 appears no foundation for the popular belief that this 



