MODERN EVOLUTION. 



197 



ceeds to work a variety of changes; and each of 

 these becomes the parent of similarly-multiplying 

 changes; the multiplication of them becoming great- 

 er in proportion as the aggregate becomes more 

 heterogeneous. And these two causes of increasing 

 differentiations are furthered by 



1 1. Segregation, which is a process tending ever 

 to separate unlike units and to bring together like 

 units — so serving continually to sharpen, or make 

 definite, dififprentiations otherwise caused. 



12. Equilibration is the final result of these trans- 

 formations which an evolving aggregate undergoes. 

 The changes go on until there is reached an equi- 

 librium between the forces which all parts of the 

 aggregate are exposed to and the forces these parts 

 oppose to them. 



Equilibration may pass through a transition stage 

 of balanced motions (as in a planetary system) or of 

 balanced functions (as in a living body) on the way 

 to ultimate equilibrium; but the state of rest in in- 

 organic bodies, or death in organic bodies, is the 

 necessary limit of the changes constituting evolution. 



13. Dissolution is the counter-change which 

 sooner or later every evolved aggregate undergoes. 

 Remaining exposed to surrounding forces that are 

 uriequilTbirated, each aggregate is ever liable to be 

 dissipated by the increase, gradual or sudden, of its 

 contained motion ; and its dissipation, quickly under- 

 gone by bodies lately animate, and slowly undergone 

 by inanimate masses, remains to be undergone at an 



