1 94 Orthoplasy 



ation of the latter — which includes the very essential de- 

 partures from recapitulation so often found in nature. 



(3) In very simple organisms, which are known as 

 * generalized ' as opposed to * specialized,' and also in 

 late stages of the development of higher animals, we find 

 least evidence of recapitulation. In the simple organisms, 

 heredity is still relatively unorganized, and the develop- 

 mental series is shorter and more direct. In higher ani- 

 mals the periods of development which ensue after birth 

 bring the animal into its independent life, in which its own 

 adjustments to the environment are of capital importance. 

 Hence no stages representing ancestral characters are pre- 

 served, except those which can exist in this separate life. 



This last case seems to find illustration in mental de- 

 velopment. We find that the series of stages of mental 

 development does not show exact recapitulation ; but that 

 omissions occur.^ In these cases variations have been 

 rigidly selected in the line of intellectual endowment and 

 educability, carrying with them increasing plasticity and 

 lessened fixity, in the nervous substance and its connec- 

 tions. This is in line with some of the great correlations 

 spoken of on an earlier page.^ With it goes also the 

 evolution of gregarious habits, family instincts, etc., by 

 which the endowment of the infancy period in the highest 

 animals is directly supplemented. 



Third, we have another reason for the fact of recapitu- 

 lation : the adaptations of hereditary endowment represent 

 most essential adjustments to environment. Nature reaches 

 them only after extended experimentation and great loss 

 of life ; really by the process of trial and error. It would 



1 See the cases cited in Mental Development, Chap. I. (especially the theory 

 of * short-cuts' in § 4). 2 chap. II. §§ 2, 3 (esp. p. 27). 



