166 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 (Amblyopsis 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 of 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 (0) 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 
afew red spots to the general coloration,as is the case in the 
British Flat-Fish Lepidorhombus megastoma. 
1 Cunningham and MacMunn, Phil. Trans. 184, 1893, -p. 765, where references 
to many other papers are given. 
