24 THE ORIGIN OF THE NERVOUS SYSTEM 



it represents such relation in its most general and 

 primitive form. While some cells and some still simpler 

 organisms may possess this pattern alone, it is certain 

 that most organisms, including all multicellular forms, 

 at least many unicellular forms and probably some of 

 those simpler than cells, possess not only a surface- 

 interior pattern but also an axiate or polar pattern and 

 primarily either a radial or bilateral symmetry with 

 asymmetric modifications in various cases. Both the 

 course of organismic evolution from very early stages 

 as well as the development of the individual are based 

 upon this axiate pattern. I have already pointed out 

 (see p. 8) that the general similarities of organismic 

 pattern in different protoplasms suggest that such 

 pattern is, at least as regards its fundamental features, 

 in large measure independent of the differences in 

 the specific constitution of different protoplasms and 

 therefore essentially quantitative, i.e., it apparently 

 represents a primarily quantitative relation in a specific 

 protoplasm. It now becomes necessary to examine the 

 data of observation and experiment with reference to 

 the question of the nature of the axiate pattern. 



Many different lines of evidence agree in indicating 

 that axiate pattern in its simplest form is essentially 

 quantitative in character and consists in graded differ- 

 ences in the rate of the fundamental dynamic activities 

 of protoplasm and in the conditions associated with 

 these activities. These graded differences in physio- 

 logical state have been called axial gradients because, 

 so far as the evidence goes, they are the primary indi- 

 cations of the existence of an axiate pattern (Child, 

 kmsO- They have also been called metabolic gra- 



