THE USES OF PHOSPHORESCENCE. 161 



a turtle and many small fishes bite readily at the deadly 

 tentacles. 



It is well known that the sunfish (Orthagoriscus), lump- 

 fish, and dogfish all attack jelly-fishes, perhaps in default of 

 better food ; and far from being afraid of light, all fishes are 

 attracted by it. It is evident, that, if jelly-fishes possess eyes, 

 they must be able to distinguish others of their kind ; hence 

 their phosphorescence may possibly be a simple signal lan- 

 guage, if so we may term it, by which they may find one 

 another ; or, having its origin in the nervous functions of 

 the animal, the light may be unconsciously emitted, and 

 have no more significance than a blush or sudden pallor 

 upon the human face. Whatever may be the value of the 

 light to themselves, it is of obvious use to other animals. It 

 assists in the general illumination of the deep recesses of 

 the ocean ; and, in the case of jelly-fishes, certainly marks 

 their position, and thus aids the whalebone whales when 

 feeding at night at depths from the surface where little light 

 penetrates. 



The various colored lights seen upon certain crustaceans 

 and worms, and their peculiar position, point to the possible 

 belief that they may be signals, constituting a primitive 

 means of communication ; also of use to the animals in light- 

 ing their way, as we have seen in the case of the pyropho- 

 rus. The lights of fishes, whatever may have been the 

 object of nature, serve several distinct purposes: to draw 

 the attention of enemies, to attract prey, and to illumine the 

 gloom about them. Any one who has fished at night by 

 torchlight well knows the attraction that light has for fishes 

 of all kinds, and when submarine electric lights have been 

 watched, groups of fishes and squids have been observed 



