220 ZOOLOGY SECT. 



pure white, the upper side dark. The eyes (r.e, I.e.) are both on 

 the upper or dark-coloured side, and the skull is distorted so as 

 to adapt the orbits to this change of position. The abdominal 

 cavity is very small, the anus placed far forward, and the dorsal 

 and ventral fins are sometimes continuous. Young Flat-fishes 

 swim in the ordinary vertical position, but after a time they lie 

 on one side and assume the adult peculiarities, the eye on the 

 lower side gradually rotating until it reaches the upper surface. 



Many Shore-fishes exhibit protective characters, the tints and 

 markings of the skin being harmonised with those of the rocks, 

 sea-weeds, &c., among which they live. The effect may be 

 heightened by fringes and lobes of skin, resembling sea-weed, and 

 often giving the fish a most grotesque appearance. The colours 

 are often adaptable : Trout, for instance, alter their colour by the 



/ c 



FIG. 893. Pleuronectes cynoglossus (Craig-fluke), from the right side. d. /. dorsal fin ; 

 1. e. left eye ; pct.f. pectoral fin ; pv.f. pelvic fin ; r. e. right eye ; v.f. ventral fin. (After 

 Cuvier.) 



contraction or expansion of their pigment-cells, according to 

 whether the streams in which they live have a muddy or a sandy 

 bottom. In some Shore-fishes, such as those of the coral reefs, 

 the colours are of the most brilliant description ; vivid reds, blues, 

 and yellows, spots or stripes of gold or silver, are common, and 

 although the combination of tints may sometimes seem to our 

 eye rather crude and glaring, they appear to be distinctly protec- 

 tive, harmonising with the brilliant hues of the Coral Polypes 

 and other members of the reef fauna. Pelagic fishes, such as the 

 Mackerel and Herring, are usually steely-blue above, white beneath. 

 Many deep-sea Teleostei are phosphorescent : in some of these 

 definite luminous organs (Fig. 894) are arranged in longitudinal 

 rows along the body, each provided with a lens and other accessory 

 parts, like those of the eye, the whole organ having the character 

 of a minute bull's-eye lantern. Some species of the same order, 



