BLIND CAVE-ANIMALS 
TRUE cave-animals—that is, those which are blind and more 
or less completely colourless, and spend their whole time 
in utter darkness—must be sharply distinguished from 
creatures like bats and owls, which take advantage of such 
situations as a temporary shelter, from which they issue 
forth at night to the outer world. And as most of these 
are more or less closely allied to animals which enjoy the 
full light of day, one of the first things that strikes one 
is why they have given up the joys of an ordinary exist- 
ence, to pass what appears to us to be a miserable life 
in total darkness. Whatever be the true explanation of 
this, it is of course easy to understand why they should 
have lost their eyes, and also the coloration characteristic 
of their outer-world relatives. 
A curious parallel exists between the inhabitants of caves 
and those creatures dwelling in the dark abysses of the 
ocean depths; both dwelling in situations entirely cut off 
from the smallest trace of daylight, and both being descended 
from animals living either in the air or water under the 
ordinary conditions. In one point, however, a remarkable 
difference exists between the two. Cave-animals, as already 
said, are content to crawl or swim in Cimmerian darkness, 
whereas the finny and other denizens of the depths of the 
ocean possess organs giving forth a brilliant phosphorescent 
light, and likewise other organs by which they can perceive 
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