THE PHYSIOLOGY OF DEEP-SEA LIFE. 311 



Avhich 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 

 livino' 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 scorpsenoids, remind us in their coloring of that of 

 their littoral allies. There is as great a diversity in color in the 

 reds, oranges, gTeens, 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 commensaHsm, 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 gorgouians, 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 aoTeeme'nt 

 in coloration in annelids when commensals upon starfishes, 

 mollusca, actiniae, or sponges, and ^^^th Crustacea, and actinise 

 parasitic upon corals, gorgonians, or moUusks. The habits of 

 the deep-sea hermit-crabs are not unhke 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 Kving 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. 



