J94 JURA. LUMINOUS ANIMALS. 



luminous, and of which the species of some, and the 

 genera, at least, of others, have also been determined. 

 But the phenomena observed by navigators on several 

 occasions, prove that animals of similar powers, whose 

 nature has not yet been investigated, abound in various 

 parts of the ocean. Cook, Perouse, Riville, Horsbrugh, 

 Newland, Langstaff, and Tuckey, have all described appear- 

 ances of the sea in which it was perfectly and permanently 

 luminous ; resembling, in some of the instances noted, a 

 vast plain of snow, or a sea of milk. Many of these 

 observers have ascertained this appearance to be produced 

 by minute animals, the nature of which however has not 

 always been described. It is probable that various animals 

 have been seen by these several persons, and that an 

 investigation of the individuals would have added many 

 more to the enumeration here given. 



The twinkling appearance that characterizes the light of 

 these worms, has been seen in water free from any visible 

 objects, if we may rely on the care and accuracy of the 

 observers ; with this only difference that the sparks were 

 more minute. Hence it was concluded that the water 

 was in these cases luminous. Three circumstances may 

 have led to errors in these observations. The slippery 

 nature of the larger Medusae causes them frequently to 

 escape when an attempt is made to lift a vessel of water 

 from the sea. The transparency also of the minuter 

 creatures enables them to elude a cursory observation; 

 and there is every probability that animals nearly micro- 

 scopic, or resembling in dimensions some of the Infusoria, 

 whether in the state of spawn or fully grown, inhabit 

 sea water; possessed of the same voluntary powers of 

 emitting light, and forming the prey of the tribes imme- 

 diately larger than themselves : the observations of Forster- 

 seem to confirm this notion. It is to these unascertained 

 beings that our attention ought to be directed ; and there 

 is little doubt that future investigations will still detect 

 many unknown and minute animals possessed of this 



