60 DARWmiANA. 



tlian tlieir parents, will cross or interbreed witli those 

 who have the same organs a little less sensitive, and 

 thus the mean standard will be kept up without any 

 advancement. If our billiard-table were sufficiently 

 extensive, i. e., infinite, the balls rolled from the cor- 

 ners would never meet, and the necessity v^hioh^Q 

 have supposed to deflect them would never act. 



The moment, however, that the want of space or 

 food commences natural selection begins. Here the 

 balls meet, and all future action is governed by neces- 

 sity. The best forms, or those nerves most sensitive 

 to light, connected with incipient membranes and hu- 

 mors for corneas and lenses, are picked out and pre- 

 served by natural selection, of necessity. All cannot 

 live and propagate, and it is a necessity, obvious to all, 

 that the weaker must perish, if the theory be true. 

 Working on, in this way, through countless genera- 

 tions, the eye is at last formed in all its beauty and 

 excellence. It must (always assuming that this the- 

 ory is true) result from this combined action of 

 natural variation, the struggle for life, and natural 

 selection, with as much certainty as the balls, after 

 collision, must pass to corners of the table different 

 from those to which they were directed, and so far 

 forth as the eye is formed by these laws, acting up- 

 ward from the nerve merely sensitive to light, we can 

 no more infer design, and from design a designer, 

 than we can infer design in the direction of the bil- 

 liard-balls after the collision. Both are sufficiently 

 accounted for by blind powers acting under a blind 

 necessity. Take away the struggle for life from the 

 one, and the collision of the balls from the other — and 



