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.