THE GREAT DEEPS 131 
on a cylindrical stalk, so that they are fitted 
for making the most of a dim light. 
Two answers to the question are possible. 
The first is, that though the animals with 
large eyes have been dredged up from the 
great depths, and probably spend most of 
their time there, they may sometimes migrate 
far enough upwards to come within the sun’s 
influence, and it is only if the eyes are never 
used at all that they tend to dwindle away. 
The second answer is, that though there is 
no daylight, there is some light from lumi- 
nescent animals. Perhaps it is this uncertain 
light which the big eyes use. 
Perhaps one of the biggest puzzles is that 
the ordinary activities of life, such as diges- 
tion and breathing, seem to go on quite 
smoothly in the great deeps, although the 
conditions of life are so very different from 
those to which the shallow-water relatives of 
the abyssal animals are accustomed. 
ORIGIN OF DEEP-SEA ANIMALS 
Where did the deep-sea animals come from? 
This is a good question, but we do not yet 
know enough to be able to answer it as we 
