804 THE AMERICAN NATURALIST. [VoL. XXXVF. 
in the warm seas, red pigment takes the place of olive. At 
a depth of 50 to 150 fathoms in the tropics a large percentage 
of the fishes are of various shades of red. Several of the large 
groupers of the West Indies are represented by two color 
forms, a shore form in which the prevailing shade is olive 
green, and a deeper water form which is crimson. In one 
case an intermediate color form also exists, which is lemon 
yellow. On the coast of California is a band-shaped blenny 
which appears in three colors, according to its surroundings, 
blood red, grass green, and olive yellow. The red coloration is 
also essentially protective, for the region inhabited by such 
forms is the zone of the rose-red alga. In the arctic waters, 
and in lakes where rose-red alga are not found, the red ground 
coloration is almost unknown, although red may appear in 
markings or in nuptial colors. It is possible that the red, both 
of fishes and alga, in deeper water is related to the effect of 
water on the waves of light, but whether this should make 
fishes red or violet has never been clearly understood. It 
is true, also, that where the red in fishes ceases violet black 
begins. 
In the great depths, from 500 to 4000 fathoms, the ground 
color in all fishes becomes deep black or violet black. This 
shade is 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 gland 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, 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. 
