Into the Depths 305 



them toward the top. If, as it appears, those forms 

 remaining permanently on the bottom originally came 

 from near the shore, and the swimming forms de- 

 scended from ancestors who swam the surface reaches, 

 it may be that the young of the latter types still find in 

 the surface ancestral conditions favorable to their de- 

 velopment. Nor is the fact that they may come for this 

 purpose in any way remarkable. The toad returns to 

 the water to spawn; the land crab goes to the sea; and 

 the eel goes back into its ancient habitat, the salt water, 

 out of regard for the welfare of its young. It is note- 

 worthy that In many of the deep-sea crustaceans, the 

 eggs grow to an enormous size before they hatch. 

 From this, and from what we know of the development 

 of the crayfish and certain land forms, it would appear 

 that the young are born at quite an advanced stage, 

 ready to lead the same life as that of the adults. In 

 this connection occurs a curious thing. Blue and green 

 colors, although not uncommon among shore or surface 

 crustaceans, are almost never seen in the species inhab- 

 iting the deep water. Yet the eggs of a large number 

 of red deep-sea crustaceans are of a brilliant blue and 

 often green. It is thought from this, therefore, that 

 the blue pigment, common in the more familiar forms 

 living at the top, is not actually absent in the deep-water 

 representatives, but merely masked by the expansion 

 of the red cells under the influence of their dark 

 surroundings. 



The feeding habits of deep-sea animals In general 

 have always been a matter of much speculation. They 

 are of necessity carnivorous ; but in the absence of vege- 

 tation, and all that it entails, it is clear that they could 



