GENESIS, HEREDITY, AND VARIATION. 355 



these plastic physiological units, which we find ourselves 

 obliged to assume, are just such more integrated, more hete- 

 rogeneous, more unstable, and more multiform molecules, as 

 would result from continuance of the steps through which 

 organic matter is reached. We see that the differentia- 

 tions of them assumed to occur in differently-conditioned 

 aggregates, and the equilibrations of them assumed to occur 

 in aggregates which maintain constant conditions, are but 

 corollaries from those universal principles implied by the 

 persistence of force. We see that the maintenance of life 

 in the successive generations of a species, becomes a con- 

 sequence of the continual incidence of new forces on the 

 species, to replace the forces that are ever being rhythmically 

 equilibrated in the propagation of the species. And we 

 thus see that these apparently-exceptional phenomena dis- 

 played in the multiplication of organic beings, fall into their 

 places as results of the general laws of Evolution. We have, 

 therefore, weighty reasons for entertaining the hypothesis 

 which affords us this interpretation. 



