in the limits over which they now range, and with the
structural peculiarities which now characterise them."

Since then a great deal of attention has been paid to the fauna of this
Mammoth cave, and also to the faunas of other dark caverns, not only in
the New, but also in the Old World. In the result, the following general
facts have been fully established.

(1) Not only fish, but many representatives of other classes, have been
found in dark caves.

(2) Wherever the caves are totally dark, all the animals are blind.

(3) If the animals live near enough to the entrance to receive some
degree of light, they may have large and lustrous eyes.

(4) In all cases the species of blind animals are closely allied to
species inhabiting the district where the caves occur; so that the blind
species inhabiting American caves are closely allied to American
species, while those inhabiting European caves are closely allied to
European species.

(5) In nearly all cases structural remnants of eyes admit of being
detected, in various degrees of obsolescence. In the case of some of the
crustaceans of the Mammoth cave the foot-stalks of the eyes are present,
although the eyes themselves are entirely absent.

Now, it is evident that all these general facts are in full agreement
with the theory of evolution, while they offer serious difficulties to
the theory of special creation. As Darwin remarks, it is hard to imagine
conditions of life more similar than those furnished by deep limestone
caverns under nearly the same climate in the two continents of America
and Europe; so that, in accordance with the theory of special creation,
very close similarity in the organizations of the two sets of faunas
might have been expected. But, instead of this, the affinities of these
two sets of faunas are with those of their respective continents--as of
course they ought to be on the theory of evolution. Again, what would
have been the sense of creating useless foot-stalks for the imaginary
support of absent eyes, not to mention all the other various grades of
degeneration in other cases? So that, upon the whole, if we agree with
the late Prof. Agassiz in regarding these cave animals as furnishing a
crucial test between the rival theories of creation and evolution, we
must further conclude that the whole body of evidence which they now
furnish is weighing on the side of evolution.

So much, then, for a few special instances of what Darwin called