DIFFICULTIES ON THEORY 167 



are only bordered by membrane. 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 corresponding 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-stating 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 vary 

 ever so little, either in habits or structure, and thus 

 gain an advantage over some other inhabitant of the 

 country, it will seize on the place of that inhabitant, 

 however different it may be from its own place. Hence 

 it will cause him no surprise that there should be 

 geese and frigate-birds with webbed feet, living on the 

 dry land or most rarely alighting on the water ; that 

 there should be long-toed corncrakes living in meadows 

 instead of in swamps ; that there should be wood- 

 peckers where not a tree grows ; that there should be 

 diving thrushes, and petrels with the habits of auks. 



Organs of extreme perfection and complication. — To 

 suppose that the eye, with all its inimitable contriv- 

 ances for adjusting the focus to different distances, for 

 admitting different amounts of light, and for the 

 correction of spherical and chromatic aberration, could 

 have been formed by natural selection, seems, I freely 

 confess, absurd in the highest possible degree. Yet 



