364 HABITS AND INSTINCTS OP ANIMALS. CHAP. XI. 



ship, produces a shallow bluish streak of light, like the 

 reflection of lightning upon the water.* 



(366.) The luminosity of FISH is a subject upon 

 which, we believe, no author has yet touched. There 

 are strong reasons, however, to believe that very many 

 of these animals possess the power of illuminating the 

 dark recesses of the ocean, if not by the same means, 

 at least with the same effect, as that produced by the 

 minute tribes we have just spoken of. When we con- 

 sider how many hundreds of species more especially 

 those which live in deep water are covered with scales 

 of a rich and shining silver hue, infinitely more brilliant 

 when these fishes are alive and in their native element, 

 than as they are commonly seen after having been caught, 

 it becomes highly probable that the brilliant radiance, 

 with which they are clothed, is to effect some other 

 purpose than mere ornament : and nothing seems more 

 probable than that such families are moving lights in 

 the bosom of the ea, at those depths through which 

 the solar light can scarcely, if at all, penetrate. In 

 favour of this supposition, it may be remarked, also, 

 that the chaetodons, the serrans, or sea perches (Ser- 

 ranincB Sw.), the gobies, blennies, and numerous other 

 groups, whose bodies, instead of being changeable sil- 

 very, are ornamented with vivid, and often dark, colours, 

 are inhabitants only of comparatively shallow waters, 

 close to the land : whereas such as have few tints, but 

 bright silvery scales, are almost exclusively found in 

 the greatest depths. Nearly the whole of the Gym- 

 netres, or riband-fish, are strong illustrations of this 

 theory. With the exception of the genera of the 

 Ophidium and Cepola, none of these fishes have any 

 colour on their bodies, or even scales ; and yet they are 

 as brilliant and shining as if they were overlaid with 

 the richest silver leaf. The different species of sun- 

 fish {fig. 89-), however, according to all writers, are 

 truly phosphorescent, and must illuminate the trackless 

 ocean in a different manner. The thick stratum of 



* Spix and Martin's Travels in Brazil, p. 44. 47. 



