234 GRAND STRATEGY OF EVOLUTION 



the outer life, and their mere increase in volume, what- 

 ever may be the cause of that increment, rather than 

 the arrangement, or the architecture of individual cells, 

 most easily and surely measures the march of organic 

 cooperation from class to class, throughout the whole 

 gamut of animal evolution, fig. 8. 



It is not surprising, therefore, that the great dif- 

 ference between man and the anthropoid apes is not so 

 easily measurable in terms of vital energy, bodily form, 

 keenness of sense, or the efficiency of any one organic 

 function, as it is in purposeful directive power, and 

 in the volume of nervous material in which that direc- 

 tive power is registered. 



That directive power, in cooperation with the 

 wholly different powers of tongue, and eye, and ear, 

 and hand, derived from a multitude of wholly differ- 

 ent organic sources, is the chief creative agency of social 

 institutions. 



IV. The Decline of Metamerism and the Centraliza- 

 tion of Functions 



We have selected these special cases to illustrate 

 the ways and means of organic progress in the arthro- 

 pod-vertebrate stock. Any of the other vital func- 

 tions, protective, excretory, sensory, or locomotor, 

 might have been used for this purpose, and would have 

 shown the same mingling of mechanical, chemical, 

 and "vital" innovations. 



But while, for the sake of convenience, the improve- 

 ments in a single system may be considered separately, 

 it must not be overlooked that each bodily system is 

 wholly dependent on, and influenced by, all the others. 



