PROGRESS 29 



increase of size of the units of life themselves (cells, 

 metazoan individuals, communities), secondly by their 

 aggregation ; and this has been accompanied by a 

 (very roughly) parallel increase in the duration of life. 



Next, there has been an increase in their complexity j 

 and this in its turn depends upon the fact that a division 

 of labour has been brought about between the parts of 

 organisms, each part becoming specialized for greater 

 efficiency in the performance of some particular 

 function. In the fewest words, the separate bits of 

 machinery of which organisms are composed have 

 become more efficient. 



In the third place, there has been an increase in the 

 harmony of these parts, and consequently in the unity 

 of the whole. Delicate mechanisms for co-ordination 

 have been developed, and arrangements whereby one 

 portion becomes dominant over the rest, and so a 

 material basis for unification is given. 



In the fourth place, there has been an increase 

 of self-regulation. The outer environment changes 

 from month to month, from hour to hour. The more 

 complex products of evolution are in high degree 

 exempt from the consequences of these changes, 

 through being the possessors of a constant internal 

 environment which, beyond the narrowest limits, 

 it is most difficult to alter. 



Fifthly, there has been an increase in the possibility 

 of bringing past experience to bear on present problems. 

 At the base is the power of modifying normal reactions 



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