100 ORGANIC EVOLUTION— THE FACTORS 



of tlic economy of nutrition acliieved ? 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 woidd amount to oVo^^^ ^^ ^^^^ creature's 

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

 to Two^^) 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 apjireciably greater multiplication of 

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



18-y). 



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 

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

 nerves are connected and co-ordinated in greater pro- 

 portion perhaps than any other organ. I i^resume 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 noimal 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 



