THE PHYSIOLOGY OF DEEP-SEA LIFE. 311 
which have flourished for long periods of time in regions far 
beyond those where protective coloration would be of ser- 
vice. We have a strong argument in favor of the gradual 
and comparatively recent migration of littoral forms into deep 
water in the fact that there are still so many vividly colored 
bathyssal animals belonging to all the classes of the animal 
kingdom, and possessing nearly all the hues found in types 
living in littoral waters. 
While we recognize the predominance of tints of white, pink, 
red, scarlet, orange, violet, purple, green, yellow, and allied col- 
ors in deep-water types, the variety of coloring among them is 
quite as striking as that of better-known marine animals. The 
fishes belonging to the lophioids, to the labroids, to the wrasses, 
and to the scorpsnoids, remind us in their coloring of that of 
their littoral allies. There is as great a diversity in color in the 
reds, oranges, greens, yellows, and scarlets of the deep-water 
starfishes and ophiurans as there is in those of our rocky or 
sandy shores. 
Among the abyssal invertebrates living in commensalism, the 
adaptation to surroundings is fully as marked as in shallow 
water. I may mention specially the many species of ophiurans, 
attached to variously colored gorgonians, branching corals, and 
stems of Pentacrinus, scarcely to be distinguished from the part 
to which they cling, so completely has their pattern of color- 
ation become identified with it. There is a similar agreement 
in coloration in annelids when commensals upon starfishes, 
mollusca, actinie, or sponges, and with crustacea, and aetinie 
parasitic upon corals, gorgonians, or mollusks. The habits of 
the deep-sea hermit-crabs are not unlike those of their shallow- 
water species, and there are deep-water pygnogonids associated. 
with hydroids. Deep-water cephalopods do not differ in their 
type of coloration from those of the coast shelf. 
The echinoids dredged beyond the hundred-fathom line are 
many of them dark-colored, but generally present, as in the case 
of the spatangoids, the neutral colors that are characteristic of 
those living at higher levels on sandy beaches, or do not differ 
in their tints from those of the littoral zone as in the case of 
the many species of Echinus proper. 
