ORGANIC EVOLUTION— THE FACTORS 101 



derived from the entire suppression of such a complex 

 organ, when it became useless, as no more than the 

 gain of so many grains of simple muscular tissue, 

 appears to me to be an extraordinary misconception of 

 the conditions of the problem." — Fortnightly Review, 

 1893, p. 655. 



But though the eye is perhaps more richly supplied 

 with muscles, blood-vessels, and nerves than any other 

 organ, yet, presumably, these structures here require the 

 same kind of nutriment as they do elsewhere in the body; 

 and since they are relatively minute they must, how- 

 ever functionally active, require a relatively minute 

 quantity of nutriment — a quantity far too little when 

 diverted to other organs to be important as a factor in 

 survival. Therefore if the nutrition supplied to the 

 eye is held to be such a drain on the resources of the 

 organism that the saving of it appreciably affects the 

 survival rate, we must suppose that the material 

 supplied to its peculiar structures is physiologically 

 extremely expensive. But as to this Mr. Spencer 

 writes — 



" If any one remembers how relatively enormous are 

 the eyes of a fish just out of the egg — a pair of eyes 

 with a body and head attached ; if he then remembers 

 that every egg contains material for such a pair of 

 eyes, he will see that eye-material constitutes a very 

 considerable part of the fish's roe ; and that, since the 

 female fish provides this quantity every year, it cannot 

 be expensive " (p. 65). 



In the proteus in particular eye-material cannot be 

 expensive, for, since the animal does not exercise 

 vision, the material is not used up, and therefore has 

 not to be replaced. I think therefore that the 



