222 TRANSITIONS OP ORGANIC BEINGS. [Chap. VI 



whereas the woodpecker of La Plata has had its structure 

 only slightly modified. In the case of the water-ouzel, 

 the acutest observer 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 swim- 

 ming? Yet there are upland geese with webbed feet 

 which rarely go near the water; and no one except Au- 

 dubon 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 fur- 

 nished 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 

 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. 



