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 deej^-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 

 adajDtation 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. As 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 Avaters of 

 moderate depths should have been retained in deep-sea types, 



^ We must except a small incrusting line in the Gulf of Mexico, as well 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. 



