100 ORGANIC EVOLUTION — THE FACTORS 



of the economy of nutrition achieved? To suppose 

 this is to suppose that the saving of a grain or two of 

 protein per day would determine the kangaroo's fate " 

 (p. 14). 



He next enters into elaborate arithmetical calcula- 

 tion concerning the eye of the proteus. " In such case 

 the decrement would amount to ^/^^th of the creature's 

 weight ; or, for convenience, let us say that it amounted 

 to lo^oft th, which would allow of the eyes being taken 

 at some fourteen grains each. To this extent then each 

 occasional decrement would profit the organism. The 

 economy in weight to a creature having nearly the same 

 specific gravity as its medium would be infinitesimal. 

 The economy in nutrition of a rudimentary organ, con- 

 sisting of passive tissues, would also be but nominal. 

 The only appreciable economy would be in the original 

 building up of the creature's structures ; and the hypo- 

 thesis of Weismann implies that the economy of this 

 thousandth part of its weight by the decrease of the 

 eyes, would so benefit the rest of the creature's organ- 

 ization as to give it an appreciably greater chance of 

 survival, and an appreciably greater multiplication of 

 descendants. Does any one accept this inference ? " (pp. 

 18-9). 



In reply to the above Mr. Wallace writes — 



" The eye is treated as if it were mere protoplasm 

 weighing so many grains, instead of being a highly 

 complex organ, with which, muscles, blood-vessels, and 

 nerves are connected and co-ordinated in greater pro- 

 portion perhaps than any other organ. I presume the 

 original eye of the ancestral proteus must have had 

 its three distinct sets of nerves — those of vision, of 

 sensation, and of motion — involving in their normal use 

 the expenditure of a considerable amount of nervous 

 energy, besides the various muscles and blood-vessels 

 •connected with it. To measure the benefit to be 



