Chap. Yl] ORGANS OF EXTREME PERFECTION. 223 



change of structure. The webbed feet of the upland 

 goose may be said to have become almost 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 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 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 varies 

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

 gains an advantage over some other inhabitant of the 

 same country, it will seize on the place of that 

 inhabitant, however different that 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 and rarely alighting on the 

 water, that there should be long-toed corncrakes, living 

 in meadows instead of in swamps ; that there should be 

 woodpeckers where hardly a tree grows ; that there 

 should be diving thrushes and diving Hymenoptera, 

 and petrels with the habits of auks. 



Organs of extreme Perfection and Complication. 



To suppose that the eye with all its inimitable 

 contrivances for adjusting the focus to different dis- 

 tances, for admitting different amounts of light, and 

 for the correction of spherical and chromatic aberration, 



