Chap. VI. 
TEANSITIONAL HABITS. 
185 
unwillingly 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 pro¬ 
foundly modified. On the other hand, the acutest ob¬ 
server 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 mem¬ 
brane. 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 cor¬ 
responding 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 re- 
