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Page:Popular Science Monthly Volume 36.djvu/403

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THE EFFECTS OF CAVE LIFE ON ANIMALS.

separate, as in the fore-foot of a quadruped, and there were even three claws, so that the animal could also grasp with its wings. 2. Its ribs were small, thin, without uncinate processes, and therefore formed no compact and solid cradle. 3. Its pelvic bones were almost like those of certain extinct reptiles. 4. Its tail was not short, with a plowshare-shaped bone and a fan-like arrangement of the tail feathers, as in all other birds, but it was long, composed of not less than twenty vertebræ, and the feathers were fixed along the whole length of this tail. In other words, it was a regular lizard tail, but covered with feathers. It is no wonder that some scientists did not consider the Archæopteryx as belonging to the birds, but thought it was a reptile. Apart from its plumage, however, there is too much in its anatomy that is avian. At any rate, it was a very reptile-like bird, and its power of flight was certainly not great. It probably fluttered more than flew, and occasionally used its claws to support itself. The formation of its eye bones seems to indicate that it was of nocturnal habits, like our owls.

Other fossils, lying as yet unknown in the strata of our earth and waiting for the ardent scientific digger, will teach us considerably more about the evolution of the birds, but the outlines of it are already mapped out by what we possess at present; and it must be said, especially about the Archæopteryx, that it sheds more light upon the development of the animal kingdom during former periods than perhaps any other known fossil.

 

THE EFFECT OF CAVE LIFE ON ANIMALS, AND ITS BEARING ON THE EVOLUTION THEORY.
By A. S. PACKARD.

THE main interest in studies on cave life centers in the obvious bearing of the facts upon the theory of descent. The conditions of existence in caverns, subterranean streams, and deep wells are so marked and unlike those which environ the great majority of organisms, that their effects on the animals which have been able to adapt themselves to such conditions at once arrest the attention of the observer. To such facts as are afforded by cave life, as well as parasitism, the philosophic biologist naturally first turns for the basis of his inductions and deductions as to the use and disuse of organs in inducing their atrophy. It is comparatively easy to trace the effects of absence of light on animals belonging to genera, families, or orders in which eyes are normally almost universally present. As we have seen in non-cavernicolous