154 Development of the Natural System. 



founded on Platonic and Aristotelian philosophy, of a plan of 

 creation and of ideal forms underlying systematic groups, 

 could not explain this discordance between morphological and 

 physiological characters. It would be easy to maintain the 

 view of the systematists, that the natural system represents 

 a plan of creation, if physiological and morphological charac- 

 ters went always truly hand in hand, if the adaptation of the 

 organs to the conditions of life in the species were perfect ; but 

 facts show that the adaptation is in the best of cases compara- 

 tively imperfect, and that it is in all cases brought about by the 

 accommodation to new requirements of organs which originally 

 served to other functions. 



