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 



322 



