NATURAL SELECTION. HI 



degree. When it was first said that the sun stood still 

 and the world turned round, the common sense of man- 

 kind declared the doctrine false ; but the old saying of 

 Voxpopuli vox Dei, as erery philosopher knows, can not 

 be trusted in science. 



p 145 Within the highest diTision of the animal 

 kingdom, namely, the Vertebrata, we can start 

 from an eye so simple that it consists, as in the lancelet, 

 of a little sac of transparent skin, furnished with a nerve 

 and lined with pigment, but destitute of any other ap- 

 paratus. In fishes and reptiles, as Owen has remarked, 

 " the range of gradations of dioptric structures is very 

 great." It is a significant fact that even in man, ac- 

 cording to the high authority of Virchow, the beau- 

 tiful crystalline lens is formed in the embryo by an ac- 

 cumulation of epidermic cells, lying in a sac-like fold 

 of the skin ; and the vitreous body is formed from em- 

 bryonic subcutaneous tissue. To arrive, however, at a 

 just conclusion regarding the formation of the eye, with 

 all its marvelous yet not absolutely perfect characters, it 

 is indispensable that the reason should conquer the im- 

 agination ; but I have felt the difiBculty far too keenly 

 to be surprised at others hesitating to extend the prin- 

 ciple of natural selection to so startling a length. 



It is scarcely possible to avoid comparing the eye with 

 a telescope. We know that this instrument has been per- 

 fected by the long-continued efforts of the highest human 

 intellects ; and we naturally infer that the eye has been 

 formed by a somewhat analogous process. But may not 

 this inference be presumptuous ? Have we any right to 

 assume that the Creator works by intellectual powers like 

 those of man ? If we must compare the eye to an optical 

 instrument, we ought in imagination to take a thick 



