THE EFFECTS OF CAVE LIFE ON ANIMALS. 389 



separate, as in the fore-foot of a quadruped, and there were even 

 three claws, so that the animal could also grasp with its win-s. 

 2. Its ribs were small, thin, without uncinate processes, and there- 

 fore 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 arrange- 

 ment of the tail feathers, as in all other birds, but it was long, 

 composed of not less than twenty vertebrse, 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 Arcliceopteryx as be- 

 longing 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 consid- 

 erably 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 Archceojoteryx, 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. PACKAKD. 



THE main interest in studies on cave life centers in the obvious 

 bearing of the facts upon the theory of descent. The condi- 

 tions 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 at- 

 tention 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 compara- 

 tively easy to trace the effects of absence of light on animals be- 

 longing to genera, families, or orders in which eyes are normally 

 almost universally present. As we have seen in non-cavernicolous 



