Organic Evolution, i8 



J 



that we mRiy pay that thn moflification of life is in the 

 direction of more or of less complete adaptation to simpler 

 or ttS^lnore complex conditionir'"''WBefe' the adaptation 

 advanxiya to nidJreljomplex conditions, we speak of elabora- 

 tion; where it retrogrades to less complex conditions, we 

 speak of degeneration; but both fall under the head of 

 evolution in its more general sense. Viewed as a whole, 

 there can be little doubt that the general tendency of 

 evolution is towards more complete adaptation to more 

 diverse and complex environment. A nd this tendency is 

 accompa nied by a general increase of differentiat ion and 

 of inte^^ tion ; of differentiation whereby the constituent 

 elemenfe^ftf life, whether cells, tissues, organs, organisms, 

 or groups of organisms, v>Q^r>TnQ pyp^vQociiYQijr more 

 specialize d and m ore different from or^ e another; of 

 integration whereby these ele ments_ hft^()p^p. prnorrAssivply 

 more int erdepen r'^'^^ nr^ on the other. We may con- 

 veniently sum up the tenden cy towards mor e perfect 

 ada ptati on to more complex circumstances in the word 

 'progress; the tendency to di fferentiation in the word 

 indi viduoE tiH and the tendenc^.Jia— uii«gration in the 

 word association. 



Nobody now doubts the propositions thus briefly sum- 

 marized, and it is therefore unnecessary to bring forward 

 evidence in their favour. 



We may pass, then, to the question — How ? Evolution 

 being continuity, associated with change, tending in certain 

 directions, and accompanied by certain processes, how has 

 it been effected ? What are its methods ? 



Natural Selection, 



Natural selection claims a foremost place. We have 

 already devoted a chapter to its consideration. Animals 

 vary ; more are born than can survive to procreate their 

 kind ; hence a struggle for existence, in which the weaker 

 and less adapted are eliminated, the stronger and better 

 adapted surviving to continue the race. 



