310 THREE CRUISES OF THE BLAKE." 
emitted by alcyonarians consisted of red, yellow, and green 
rays only. 
* Hence, were the light in the deep sea derived from this source, in 
the absence of blue and violet, only red, yellow, and green colors could 
be effective. . . . A brilliant green coloring-matter was found in some 
deep-sea Annelids. No doubt in many cases the coloring of the deep- 
sea animals, as in the case of the purple Holothurians, is useless, and 
only a case of persistence. The madder coloring of some of the soft 
parts of the Corals may be in like case, but possibly useful for at- 
traction of prey, being visible by the phosphorescent light. . . . 
“The same coloring-matters exist in deep-sea animals which are 
found in shallow-water forms. In the case of deep-sea possessors 
of these pigments, they perhaps never exercise their peculiar complex 
action on light during the whole life of the animal, but remain in dark- 
ness, never showing their color.” 
Many of the deep-sea fishes collected by the “Blake” are of 
a grayish color, or a dull black, or have as it were lost their 
color, and been bleached to a dirty white; they resemble in 
this respect semi-transparent fish embryos, in which black is still 
the most characteristic pigment. No blue animals have been 
noticed among the deep-sea types ; blue is, in spite of its appar- 
ent protective color, rarely seen in marine animals, except in a 
few pelagic forms. Deep-sea burrowing animals have fully as 
marked a diversity of coloring as their shallower water con- 
geners. There is apparently in the abysses of the sea the same 
adaptation to the surroundings as upon the littoral zone. We 
meet with highly colored ophiurans within masses of sponges, 
themselves brilliantly colored, at a depth of more than 150 
fathoms. 
Again, other ophiurans, coming from the globigerina ooze, 
could hardly be seen when stretched out on its surface. Ag in 
shallower waters, they must live buried in this material, from 
which they can scarcely be distinguished. It seems difficult to 
believe that protective characters which are of use in waters of 
moderate depths should have been retained in deep-sea types, 
1 We must except a small incrusting line in the Gulf of Mexico, as weil as blue 
sponge of a blue color, not uncommon in eggs of a crustacean living buried in large 
the dredgings near the hundred-fathom masses of Sponge. 
