67 



minate the fluid mass ; agitation did not restore the 

 effect, though a few drops of acid caused a solitary gem 

 to twinkle. In the estimate of this phenomenon, we 

 scarcely know whether to ascribe it to the presence of 

 the pyrosom pygmcea, studded with luminous young, 

 or salpcB. It might be the latter that were vested with 

 this brilliant and beautiful ornament ; and we presume 

 that these living fires were subsequently, by the me- 

 chanical agitation, separated from their attachment, 

 and might be luminous ova or young. On transfer- 

 ing a luminous medusa, taken off the mouth of the 

 river Nen, on the coast of Norfolk, to a glass of 

 fresh water, the luminous matter in its descent con- 

 tracted like a purse-mouth. It seems quite certain, 

 therefore, that the luminosity of the sea is a pheno- 

 menon dependent on the presence of luminous marine 

 animals. The following interesting description, 

 in further corroboration of the opinion, is extracted 

 from Tuckey's " Narrative of an Expedition, &c.* :" 

 " The cancer fulgens was conspicuous ; in another 

 species, when put into the microscope by candle-light, 

 the luminous matter was observed to be in the brain, 

 which, when the animal was at rest, resembled a most 

 brilliant amythest, about the size of a large pin's head, 

 and from which, when it moved, darted flashes of a 

 brilliant silvery light. Beroes, beautiful holothurias, 

 and various gelatinous animals, were also taken up in 

 great numbers. Indeed, the Gulf of Guinea appears 

 to be a most prolific region in this sort of animals." 



The late Professor Smith, of Christiana, considered 

 that the luminous appearance which diffuses itself over 

 the whole surface of the sea, in the Atlantic, arose 

 from a dissolved slimy matter ; and that the most 

 minute glittering particles, when highly magnified, had 



* London, 4to. 1818. p. 49. 



