PROBLEM OF CAVE BLINDNESS 247 
some frailty of constitution or by having fallen 
behind the times. Some are relices of a Glacial 
fauna. Their closest analogues are to be found 
among the shy “cryptozoic” creatures who hide 
under stones and bark and seldom venture forth. 
The true cave-dwellers are more or less adapted to 
the permanent conditions—darkness, constant tem- 
perature, humid atmosphere, and absence of green 
plants. They include (apart from bats and mice) 
the weird Amphibian Proteus of the great caves of 
Carniola and Dalmatia, three or four North Amer- 
ican salamanders, quite a lot of small fishes, a few 
snails, numerous beetles and a sprinkling of other 
kinds of insects, many spiders (who insinuate them- 
selves everywhere), and a few Crustaceans, besides 
some still smaller deer. After making sundry reser- 
vations, we recognize that those cavernicolous ani- 
mals that have open-air relatives with which they 
may be compared tend to be dwarfish, to be mo- 
notonous or deficient in coloration, to have ex- 
quisitely developed tactility, and to have more or 
less rudimentary eyes. It is on this tendency to- 
wards blindness that we wish to focus attention. 
There are considerable differences in the degree of 
degeneration which the eyes of cave animals exhibit, 
but there are few that have remained unaffected. In 
the pale Proteus, which has no pigment in its skin, 
the eye is without a lens and does not reach the 
surface of the head. This reminds us of the buried 
eye of the deep-water hagfish and of the way in 
which the very lids of the eyes of the Cape Golden 
