nwillingly it takes flight, would be mistaken by any one
for an auk or grebe; nevertheless, it is essentially a petrel, but with
many parts of its organisation profoundly modified. On the other hand,
the acutest observer by examining the dead body of the water-ouzel would
never have suspected its sub-aquatic habits; yet this anomalous
member of the strictly terrestrial thrush family wholly subsists by
diving,--grasping the stones with its feet and using its wings under
water.

He who believes that each being has been created as we now see it, must
occasionally have felt surprise when he has met with an animal having
habits and structure not at all in agreement. What can be plainer than
that the webbed feet of ducks and geese are formed for swimming? yet
there are upland geese with webbed feet which rarely or never go near
the water; and no one except Audubon has seen the frigate-bird, which
has all its four toes webbed, alight on the surface of the sea. On the
other hand, grebes and coots are eminently aquatic, although their toes
are only bordered by membrane. What seems plainer than that the long
toes of grallatores are formed for walking over swamps and floating
plants, yet the water-hen is nearly as aquatic as the coot; and the
landrail nearly as terrestrial as the quail or partridge. In such
cases, and many others could be given, habits have changed without a
corresponding change of structure. The webbed feet of the upland goose
may be said to have become rudimentary in function, though not in
structure. In the frigate-bird, the deeply-scooped membrane between the
toes shows that structure has begun to change.

He who believes in separate and innumerable acts of creation will say,
that in these cases it has pleased the Creator to cause a being of one
type to take the place of one of another type; but this seems to me
only restating the fact in dignified language. He who believes in the
struggle for existence and in the principle of natural selection, will
acknowledge that every organic being is constantly endeavouring to
increase in numbers; and that if any one being vary ever so little,
either in habits or structure, and thus gain an advantage over some
other inhabitant of the country, it will seize on the place of that
inhabitant, however different it may be from its own place. Hence it
will cause him no surprise that there should be geese and frigate-birds
with webbed feet, either living on the dry land or most