164 FISHES CHAP. 



complex system of branching grooves or of deeply-seated and 

 externally inconspicuous canals. The course of the lateral line 

 can, as a rule, readily be detected by the naked eye, and, even 

 when not otherwise distinguishable, may be traced by the series 

 of simple or multiple pores through which, at intervals, the 

 canal communicates with the exterior (Fig. 93, A), and often also, 

 in the trunk and tail, by a band of coloration different to that of 

 the rest of the body. 



Coloration. 



Contrary to popular opinion, it may be doubted if any 

 animals, even Insects or Birds, can vie with living Fishes in the 

 brilliancy and changeability of their colours. The nature of 

 their habitat, the rapid fading of the natural tints after death, 

 and the fact that museum specimens, however carefully pre- 

 served, afford but a ghostly resemblance to the colours of the living 

 animal, account, no doubt, for much of the prevalent ignorance 

 of the extraordinary extent to which colour-development may 

 proceed in a considerable number of Fishes. Like the generality 

 of northern forms of life, the Fishes of our own seas, rivers and 

 lakes, are less conspicuous for vivid and striking coloration than 

 those of tropical or subtropical climes, although such familiar 

 Teleostean Fishes of our seas and fresh waters as the Mackerel, the 

 Salmon and Trout, the males of the Stickleback and Dragonet, 

 some of the Gurnards (Triglidae) and Wrasses (Labridae), the 

 Opah or King-Fish (Lampris luna), and many others, are notable 

 exceptions. Brilliancy of coloration is most conspicuous in the 

 Teleostei : in nearly all other Fishes the colours are more uniform, 

 usually sober and often sombre, with no more variety than is 

 afforded by the presence of dark spots or bands on a lighter 

 ground, or vice versd, or by the lighter colour of the ventral as 

 compared with the dorsal surface. In Teleosts all the resources 

 of colour -formation, pigmentation, reflection, and iridescence 

 through optical interference, in diverse combinations, are employed 

 in the production of the various tints, while the dominant ground 

 colour is often diversified by the presence of stripes, bands or 

 bars, longitudinal or transverse, or of spots of different hues, 

 frequently arranged in striking and intricate patterns. 



The possibilities of coloration in these Fishes may be briefly 

 illustrated by a few examples : 



