134 ORGANS OF EXTREME PERFECTION. [CHAP. VI. 



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 

 r, 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 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 degree. When it was first 

 said that the sun stood still and the world turned round, the 

 .common sense of mankind declared the doctrine false ; but the old 

 saying of Vox populi, vox Dei, as every philosopher knows, can- 

 not be trusted in science. Reason tells me, that if numerous 

 gradations from a simple and imperfect eye to one complex and 

 perfect can be shown to exist, each grade being useful to its 

 possessor, as is certainly the case ; if further, the eye ever varies 

 and the variations be inherited, as is likewise certainly the case ; 

 \j and if such variations should be useful to any animal under 

 changing conditions of life, then the difficulty of believing that a 

 perfect and complex eye could be formed by natural selection, 

 though insuperable by our imagination, should not be considered 

 as subversive of the theory. How a nerve comes to be sensitive 

 to light, hardly concerns us more than how life itself originated ; 

 but I may remark that, as some of the lowest organisms, in which 

 nerves cannot be detected, are capable of perceiving light, it does 

 not seem impossible that certain sensitive elements in their 

 sarcode should become aggregated and developed into nerves, 

 endowed with this special sensibility. 



In searching for the gradations through which an organ in any 

 species has been perfected, we ought to look exclusively to its 

 lineal progenitors ; but this is scarcely ever possible, and we are 

 forced to look to other species and genera of the same group, that 

 is to the collateral descendants from the same parent-form, in 

 order to see what gradations are possible, and for the chance of 

 some gradations having been transmitted in an unaltered or little 

 altered condition. But the state of the same organ in distinct 



