CHAP. VI.] TRANSITIONS OF ORGANIC BEINtiS. 133 



by De Saussure as boring holes into hard wood in order to lay up 

 a store of acorna 



Petrels are the most aerial and oceanic of birds, but in the quiet 

 sounds of Tierra del Fuego, the Putfinuria berardi, in its general 

 habits, in its astonishing power cf diving, in its manner of swim- 

 ming and of Hying when made to take Hight, would be mistaken 

 by any one for an auk or a grebe ; nevertheless it is essentially a 

 petrel, but with many parts of its organisation profoundly modified 

 in relation to its new habits of life ; 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 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 walk- 

 ing 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 a.s 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 rudi- 

 mentary in function, though not in structure. In the frigate-bird, 

 the deeply scooped membrane between the toes shows that struc- 

 ture 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 re-stating tke fact in dignified 

 language. He who believes in the struggle for existence and in 



