52 THE ORGANIC GROWTH OF THE LIVING WORLD SEC. 



will it be in a condition to maintain the persistent characters 

 in face of the coercive powers of adaptation, and these latter 

 will be thrown on to other characters with greater modifying 

 effect." 



ELABORATION AND SIMPLIFICATION IN THE EVOLUTION OF 

 SPECIES 



I come now to the second of the questions previously 

 formulated, to the question, On what grounds each species 

 high in the scale of evolution was able to surpass the one 

 next below it what are the causes of increased perfection ? 



This advance in structure in the organic world is most 

 clearly revealed by the examination of the development of 

 some one individual organism so long as it be not a 

 degenerated form. The individual in this development 

 passes by growth through the series of its ancestors, but it 

 grows a stage farther on to the condition which constitutes 

 its individuality, which distinguishes it from the next lower 

 stage. 



Nageli calls in the aid of a " principle of improvement." 



I assume with him that the conditions for a progress 

 towards the more complex and towards division of labour 

 exist in the fact that a higher stage once reached can afford 

 a foundation for one still higher, since the former, the 

 existing stage, will necessarily be the starting-point for 

 further modification. 



Nevertheless, my view has certainly nothing to do with a 

 " principle of increasing perfection " in Nageli's sense. I 

 confess that with respect to the criticism of this foundation 

 of Nageli's theory I count myself among those whom its 

 author describes as the " less far-sighted," at least in so far as 

 I consider the assumption of such a principle acting in 

 accordance with organic persistence of motion as merely an 



