228 ORGANS OP EXTREME PERFECTION. [Chap. VI. 



highest human intellects;- and we naturally infer that 

 the eye has been formed by a somewhat analogous pro- 

 cess. But may not this inference be presumptuous? 

 Have we any right to assume that the Creator works by 

 intellectual powers Hke those of man? If we must 

 compare the eye to an optical instrument, we ought in 

 imagination to take a thick layer of transparent tissue, 

 with spaces filled with fluid, and with a nerve sensitive 

 to light beneath, and then suppose every part of this 

 layer to be continually changing slowly in density, so as 

 to separate into layers of different densities and thick- 

 nesses, placed at different distances from each other, 

 and with the surfaces of each layer slowly changing in 

 form. Further we must suppose that there is a power, 

 represented by natural selection or the survival of the 

 fittest, always intently watching each slight alteration 

 in the transparent layers; and carefully preserving each 

 which, under varied circumstances, in any way or in 

 any degree, tends to produce a distincter image. We 

 must suppose each new state of the instrument to be 

 multiplied by the million; each to be preserved until 

 a better one is produced, and then the old ones to be all 

 destroyed. In living bodies, variation will cause the 

 slight alterations, generation will multiply them almost 

 infinitely, and natural selection will pick out with un- 

 erring skill each improvement. Let this process go on 

 for millions of years; and during each year on millions of 

 individuals of many kinds; and may we not believe that 

 a living optical instrument might thus be formed as 

 superior to one of glass, as the works of the Creator are 

 to those of man? 



