a 
185 
brought about only very gradually—in the course of thousands of 
generations.* 
’. But we have blind animals nearer to us than those found in 
the Kentucky cave. Look at the mole, whose eyes are so 
extremely small, and so overgrown with skin and fur, that they 
are virtually no eyes at all. Yet the species, or its ancestors, 
must once have had eyes, for they are very conspicuous even now 
in the young state previous to birth, and in fact larger than 
in the adult, being a case of atavism, or a survival in part, of the 
characters of a pre-existent form from which our mole has been 
derived. What brought about the change may have been an 
increasing desire for worms, which is now its chief food, and 
which could never have been obtained in sufficient quantity to 
satisfy its voracious appetite without hunting them up in their 
own quarters. This altered habit would lead to the construction 
of those underground galleries with which we are so familiar; 
and seldom coming above ground except by accident, eyes would 
not be wanted, and from long disuse they would become almost 
obliterated as we now find them. I may add, in proof of the 
mole’s voracity, that if shut up in a box, even after a full repast, 
without a supply of food, it has been said to die of starvation in 
a few hours. 
I spoke just now of the sureness and facility with which the 
blind fish in the Kentucky cave, notwithstanding their blindness, 
regulate their movements in the water. It is a curious circum- 
stance that the mole, which has also lost its eyes, is possessed of 
some instinctive faculty, by which it not only makes its way 
underground, but can likewise find a passage, when desired, across 
waters. There is a case on record, in which a mole was 
_ *Those who are interested in the subject of the Mammoth Cave.of 
Kentucky and its remarkable Fauna, should consult the 5th, and one 
or two succeeding volumes of Nature, where they will find further 
details with Illustrations. 
