THEORY OF EVOLUTION. 43 



Thereafter more complex life-forces, owing 

 existence to the same constructive Power 

 as the first, successively evolved new org- 

 anisms, widely diversified in form, and, as 

 a rule, more and more highly specialised, 

 until the evolution culminated in Man. 



In the process of evolution the Specific 

 life -force of an existing organism was 

 utilised in evolving a new type, so far as 

 the old and the new were alike : in other 

 words, the new structure was built on old 

 foundations. 



Evolution was not invariably towards 

 higher specialisation, nor was it restricted 

 to one line of development. Like a lofty, 

 wide -spreading tree, the main stem of 

 evolution put forth branches in all direc- 

 tions, some more or less divergent from the 

 upright trunk, others horizontal, and not a 

 few downwards ; but the evolution through- 

 out was on the same principles develop- 

 ment by utilising, as far as serviceable, 

 the Specific life -force of an existing type 

 to evolve a new, and, growth by accretion 

 of cells. 



The differentiation between successive 

 types was effected by modifying, or add- 

 ing to, an existing Specific life-force. 



Thus not only every species, but every 



