Criticisms of Theory of Natural Selection. 353 



And being thus useful from the very moment of its 

 inception, it would afterwards be gradually improved 

 as variations of more and more utility presented them- 

 selves, until not only would finer and finer degrees of 

 difference between light and shade become perceptible, 

 but even the outlines of solid bodies would begin to 

 be appreciated. And so on, stage by stage, till from 

 an ordinary nerve-ending in the skin is evolved the 

 eye of an eagle. 



Moreover, in this particular instance there is very 

 good reason to suppose that the modification of the 

 cutaneous nerves in question began by a progressive 

 increase in their sensitiveness to temperature. Wher- 

 ever dark pigment happened to be deposited in the 

 skin and we know that in all animals it is apt to be 

 deposited in points and patches, as it were by accident, 

 or without any "prophecy" as to future uses, the 

 cutaneous nerves in its vicinity would be better able 

 to appreciate the difference between sun and shade in 

 respect of temperature, even though as yet there were 

 no change at all in these cutaneous nerves tending to 

 make them responsive to light. Now it is easy to see 

 how, from such a purely accidental beginning, natural 

 selection would have had from the first sufficient 

 material to act upon. It being of advantage to a 

 lowly creature that it should distinguish with more 

 and more delicacy, or with more and more rapidity, 

 between light and darkness by means of its thermal 

 sensations, the pigment spots in the skin would be 

 rendered permanent by natural selection, while the 

 nerves in that region would by the same agency 

 be rendered more and more specialized as organs 

 adapted to perceive changes of temperature, uatil 



* A a 



