XXXII 

 PROBLEM OF CAVE BLINDNESS 



PRE-EMINENT as man is, compared with 

 other creatures, there are few of the deeper 

 problems of Natural History which have not a 

 practical bearing on human affairs. The touch of 

 animate protoplasm makes the whole living world 

 kin; and if we knew with certainty how it has come 

 about that many cave-animals are blind or have ill- 

 developed eyes, we should be able to think more 

 clearly in regard to some dwellers in darkness 

 nearer home. Let us turn, then, sympathetically 

 to the fact of cave blindness, and to some notable 

 recent contributions to the evolutionary problem 

 which it raises. Dry caves have never more than 

 casual tenants, but damp caves harbor many 

 creatures from salamanders to wood-lice which 

 are in the strict sense at home there. The list of 

 Troglodytes is more extensive than honorable, for 

 leaving out of account the numerous bats and a few 

 peculiar mice, which rest in the cave but feed by 

 night outside of it, thus making the best of two dark 

 worlds, we find that the bulk of the cavernicolous 

 fauna is rather weedy. There are few cave-dwelling 

 animals of the desperado type that we associate 

 ;with Adullam; most of them are handicapped by 



