88 THE MAMMOTH CAVE. 
The fish are of a peculiar species, and are of 
a class known as viviparous, which give birth to 
their young alive, and do not deposit eggs after 
the manner of most other fish. They have ru- 
diments of eyes, but no optic nerve, and are 
therefore incaprble of being affected by any de- 
cree of light. We are indebted to Dr. Wright, 
who is perfectly familiar with the facts, for this — 
statement. 
The eyeless crawfish give birth to their young 
in the same manner as those provided with eyes. 
Both the fish and the crawfish are of a color 
almost white. 
Ordinary fish and crawfish are sometimes 
washed into the Cave from Green River. Frogs, 
also, are occasionally washed into Echo River, 
and, at times, may be heard croaking to the 
echo of their own voices.. 
It has been proven that the eyeless fish prey 
upon each other. In shape they somewhat re- 
semble the common catfish, and rarely exceed 
eight inches in length. One of these fish was 
caught by the guide in our presence, placed in 
a bottle of water, and taken out of the Cave 
alive, and might have been brought home with: 
us, without impairing its vitality, if supplied 
daily with fresh water. They are captured by 
