they came to a portion of the floor of the cave carefully railed in. Within the enclosure the guides pointed out several prints of moccasoned feet upon the soft dust, which he said had been there since the cave was discovered. The whole floor was found thickly covered with similar tracks, which, of course, were soon obliterated by the feet of visitors, and these alone had been preserved. They are supposed to have been made by the Indians, whose acquaintance with the cave seems to be beyond a doubt. The professor carefully examined the tracks within the railed enclosure. They were four or five in number, small and well-shaped, and the toes turned inward, a well-known peculiarity of the Indian gait. The doctor groped about among the crevices between the rocks, and presently returned with several small bits of wood, which he handed to the professor. On examination, they were found to be fragments of hickory bark, and every one was charred at one end. "These," said the doctor, "are probably the remains of the torches by which the Indians explored the cave. The loose, dry scales of this bark," he explained, "burn with a clear, white flame, and are quite as good for torches as pitch-pine knots."
A few hundred feet further on the guides pointed out a ledge of rock in which were several thin seams of fine black flint. These had been chipped off down to the surface of the soft matrix in which they were imbedded, and the floor beneath was covered with small fragments. This, they said, it was supposed had been done by the Indians, the suitable pieces used for spear and arrow heads, and the useless fragments left upon the spot.
Still further on is a large, shallow pool, supplied by a spring in the side of the cavern. The professor groped and paddled in the shallow water, examining the bottom and turning over stones a considerable time, while the rest of the party walked on. At length he overtook them, carefully holding in his hand a small object, which he seemed to regard with great exultation. It was a small crawfish, wholly destitute of eyes, and its substance white and translucent.
"This," said the professor, " is a species of the genus Astacus, found only in subterranean waters. Its whiteness is owing to the absence of light, which is an essential condition of color in all organic forms, animal as well as vegetable. The absence of visual organs is a singular example of natural adaptation to peculiar conditions. As no ray of light ever penetrates its habitation, eyes would be superfluous and useless."
"How was it with the ancestors of this crawfish?" asked the doctor. "Did the primeval Astacus, the remote progenitor of this white-livered individual, have eyes?"
"That is one theory," replied the professor. "But I rather incline to the hypothesis of special creations for special conditions and localities. Immutability of species is the general law of reproduction. Attempts have been made to establish exceptions to it, but I have never met with any satisfactory evidence. I rather think the first member of the species to which this creature belongs was precisely like him, and may have been created millions of years ago. There is a system of streams and rivers, ponds and lakes in the rocks beneath our feet as well as on the surface; and the conditions of life may be as favorable to the Astacus in the waters under the earth as to his more fortunate cousins in the waters above." The professor stopped short and looked a little confused. In his enthusiasm he had forgotten himself, and thought he was lecturing to his class.
The guides now announced that the spot on which they stood was the most re-
