not only altogether bird-like, but have the special characters
of the feet of perching birds, while the body had a clothing of true
feathers. Nevertheless, in some other respects, _Archaeopteryx_ is
unlike a bird and like a reptile. There is a long tail composed of many
vertebrae. The structure of the wing differs in some very remarkable
respects from that which it presents in a true bird. In the latter, the
end of the wing answers to the thumb and two fingers of my hand; but
the metacarpal bones, or those which answer to the bones of the fingers
which lie in the palm of the hand, are fused together into one mass; and
the whole apparatus, except the last joints of the thumb, is bound up in
a sheath of integument, while the edge of the hand carries the principal
quill-feathers. In the _Archaeopteryx,_ the upper-arm bone is like that
of a bird; and the two bones of the forearm are more or less like those
of a bird, but the fingers are not bound together--they are free. What
their number may have been is uncertain; but several, if not all,
of them were terminated by strong curved claws, not like such as are
sometimes found in birds, but such as reptiles possess; so that, in the
_Archaeopteryx,_ we have an animal which, to a certain extent, occupies
a midway place between a bird and a reptile. It is a bird so far as
its foot and sundry other parts of its skeleton are concerned; it is
essentially and thoroughly a bird by its feathers; but it is much more
properly a reptile in the fact that the region which represents the
hand has separate bones, with claws resembling those which terminate the
forelimb of a reptile. Moreover, it has a long reptile-like tail with
a fringe of feathers on each side; while, in all true birds hitherto
known, the tail is relatively short, and the vertebrae which constitute
its skeleton are generally peculiarly modified.

Like the _Anoplotherium_ and the _Palaeotherium,_ therefore,
_Archaeopteryx_ tends to fill up the interval between groups which, in
the existing world, are widely separated, and to destroy the value
of the definitions of zoological groups based upon our knowledge of
existing forms. And such cases as these constitute evidence in favour
of evolution, in so far as they prove that, in former periods of the
world's history, there were animals which overstepped the bounds of
existing groups, and tended to merge them into larger assemblages. They
show that animal organisation is more flex