1 66 FISHES CHAP. 



form an irregular spiral pattern. In both sexes the pattern of 

 the longitudinal bands is never precisely the same in any two 

 individuals. Scarcely less brilliant is the coloration of those 

 Teleosts, notably species of Pomacentridae and Chaetodontidae, 

 which frequent the coral reefs of the East Indian Archipelago 

 and the Pacific and feed on the coral polypes, and of many 

 of the Wrasses (Labridae). Many other groups, such, for 

 example, as the Percidae, Cirrhitinae, and the Pipe-Fishes 

 (Syngnathidae), include species in which the coloration is vivid 

 and often beautiful, although less striking than is the case with 

 the Fishes mentioned above. As illustrating the opposite 

 extreme in the scale of coloration, between which and the 

 brilliant tints just described every conceivable gradation exists, 

 mention may be made of the colourless appearance of those Fishes 

 which, like the Kentuckian Blind-Fish {Amhlyopsis spelaea), are 

 denizens of subterranean rivers ; and, omitting a few species in 

 which the coloration is almost brilliant, the prevalent sombre 

 tints, dark brown or black, rarely relieved by spots, bands, or 

 other distinctive markings, of the Fishes inhabiting the abyssal 

 waters qf the deep sea. 



The coloration of Fishes is due to the presence in the dermic 

 portion of the skin of (a) special pigment-containing cells (colour- 

 sacs, chromoblasts or chromatophores), and (&) a peculiar reflecting 

 tissue composed of iridocytes.-' Chromatophores are probably 

 branched connective-tissue cells in which pigments of various 

 colours are deposited. The colouring matter present in different 

 chromatophores is red, orange, and yellow, all of which belong to 

 the lipochrome group of pigments, or black (melanin group), but 

 by the combination or blending of differently-coloured chromato- 

 phores other colours may be produced. Thus, green results from 

 the mixing of yellow and black in suitable proportions ; brown 

 from the blending of yellow and black ; and other shades or 

 tints from an appropriate mixture of chromatophores of various 

 colours. As a rule the muscles of Fishes contain but little 

 haemoglobin, but, when visible through the skin, the occasional 

 presence of this substance in localised patches may contribute 

 a few red spots to the general coloration, as is the case in the 

 British Fiat-Fish Lejndorhombus megastoma. 



^ Cunningham and MacMunn, Phil. Trans. 184, 1893, p. 765, where references 

 to many other papers are given. 



