The Colors of Fishes 81 
stood. It is true also that where the red in fishes ceases violet- 
black begins. 
In the greater depths, from 500 to 4000 fathoms, the ground 
color in most fishes becomes deep black or violet-black, sometimes 
with silvery luster reflected from the scales, but more usually 
dull and lusterless. This shade may be also protective. In 
these depths the sun’s rays scarcely penetrate, and the fish and 
the water are of the same apparent shade, for black coloration 
is here the mere absence of light. 
In general, the markings of various sorts grow less distinct 
with the increase of depth. Bright-red fishes of the depths are 
usually uniform red. The violet-black fishes of the oceanic 
abysses show no markings whatever (luminous glands excepted), 
and in deep waters there are no nuptial or sexual differences in 
color. 
Ground colors other than olive-green, gray, brown, or silvery 
rarely appear among fresh-water fishes. Marine fishes in the 
tropics sometimes show as ground color bright blue, grass- 
green, crimson, orange-yellow, or black; but these showy colors 
are almost confined to fishes of the coral reefs, where they are 
often associated with elaborate systems of markings. 
Protective Markings.—The markings of fishes are of alrnost 
every conceivable character. They may be roughly grouped 
as protective coloration, sexual coloration, nuptial coloration, 
recognition colors, and ornamentation, if we may use the latter 
term for brilliant hues which serve no obvious purpose to the 
fish itself. 
Examples of protective markings may be seen everywhere. 
The flounder which lies on the sand has its upper surface cov- 
ered with sand-like blotches, and these again will vary according 
to the kind of sand it imitates. It may be true sand or crushed 
coral or the detritus of lava, in any case perfectly imitated. 
Equally closely will the markings on a fish correspond with 
rock surroundings. With granite rocks we find an elaborate 
series of granitic markings, with coral rocks another series of 
shades, and if red corals be present, red shades of like appear- 
ance are found on the fish. Still another kind of mark indi- 
cates rock pools lined with the red calcareous alge called coral- 
lina. Black species are found in lava masses, grass-green ones 
