CONNECTING AND MISSING LINKS
resented, one by a single feather and the other two by complete skeletons, except that one is headless. This headless form, now in the British Museum of Natural History, is the famed Archaeopteryx; the other, in Berlin, shows sufficient distinction in its preserved parts to warrant a new generic name, Archaeornis. Both are classed as birds largely because of the feathers and implied powers of flight; in other respect they are reptiles. Archaeornis, in fact, has been called a reptile in the disguise of a bird, and the skull might well belong to a reptile, never to a modern bird. Here a none too efficient flight is already attained, but here again the history is missing, and our ideas concerning the origin of bird flight must still remain hypothetical. The scientific visualization of this pro-avian is of a light-built dinosaur-like form, running freely on the hind limbs and occasionally taking to trees for soaring leaps, sustained largely by partly modified reptilian scales. Out of such a scale in turn would evolve that masterpiece of nature, the feather—a prophecy that may in time be realized by fortunate discovery in the older rocks. From Archaeopteryx to the toothed birds of the Cretaceous period is again a considerable unbridged gap, during which the bird became essentially modernized except for the retention of teeth in the jaws, which may well have been due, however, to a habit of eating fish. We can well imagine intervening stages, showing gradual adaptation to greater efficiency in flying. The shortening of the lizard-like tail of Archaeornis, the feathers of which are arranged in a row on either side, to the fan-like tail of the pigeon or crow produced a vastly better device for manoeuvering in flight. The hand has consolidated the old free grasping fingers into a better and stronger wing, and the skull has changed its character in many details. A succession of drawings comparable to a moving picture film might well be made to show these
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