CHAPTER X 

 DEVOLUTION 



GROWTH is usually contrasted with death, for 

 when the period of growth ends the decay 

 begins that ends in death. Growth should, 

 however, be contrasted with devolution a 

 tendency of complex organisms to break up 

 into parts. Even if this rupture is accom- 

 panied by decay of the organism, regeneration 

 may take place if there is a sound core in 

 either part, and the organism be brought back 

 to its former vigor. At least this is true of 

 many animals, and if the preceding argument 

 is correct, the principle holds for all organ- 

 isms. Growth is not a steady process. There 

 are periods of increasing specialization, of de- 

 specialization, and of simplification, these in 

 turn being followed by regeneration and new 

 growth. The regeneration of parts follows 

 unless the disruption prevents access to nutri- 



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