128 THE ORIGIN OF THE NERVOUS SYSTEM 



condition at higher levels. In other words, the primi- 

 tive type of axiate physiological integration is similar 

 to the autocracy in social integration, but in the devel- 

 opment and evolution of the organism, as in social 

 development and evolution, there is a gradual approach 

 toward democracy. 



While the evidence is less extensive, the data of 

 normal development and of experiment indicate that 

 the ontogenetic relation of the postcephalic regions of 

 the central nervous system to regions lateral and dorsal 

 (invertebrates) or ventral (vertebrates) to them is 

 similar to the relation of the cephalic to the post- 

 cephalic regions. These postcephalic regions of the 

 central nervous system apparently arise from the high 

 ends of the symmetry gradients (Figs. 13-17), and so 

 far as these regions are dominant they must be primarily 

 independent of the parts which they dominate. 



THE SIGNIFICANCE OF THE FACTS 



It is a fact of considerable theoretical interest not 

 merely to the biologist but to the psychologist as well 

 that the cephalic region of the central nervous system 

 arises from that region of the body which primarily is 

 most intensely active and most completely independent 

 of other parts. In fact the development of the central 

 nervous system and particularly of its cephalic portion 

 represents that physiological and morphological reaction 

 of animal protoplasm which is least complicated by 

 physiological correlation with other parts and most 

 directly related to external exciting factors. The cen- 

 tral nervous system arises from the higher levels of the 

 chief axial gradients in the organism, and these represent 



