ver, by examining its dead body, would never have suspected
its sub-aquatic habits; yet this bird, which is allied to the thrush
family, subsists by diving,--using its wings under water and
grasping stones with its feet. All the members of the great order of
Hymenopterous insects are terrestrial, excepting the genus Proctotrupes,
which Sir John Lubbock has discovered to be aquatic in its habits; it
often enters the water and dives about by the use not of its legs but of
its wings, and remains as long as four hours beneath the surface; yet
it exhibits no modification in structure in accordance with its abnormal
habits.

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 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 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 ocean. 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, not furnished
with membrane, of the Grallatores, are formed for walking over swamps
and floating plants. The water-hen and landrail are members of this
order, yet the first is nearly as aquatic as the coot, and the second is
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 almost 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 may say,
that in these cases it has pleased the Creator to cause a being of one
type to take the place of one belonging to 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 varies ever so little,
either in habits or structure, and thus gains an advantage over some
other inhabitant of the sam