66 THE ORIGIN OF THE NERVOUS SYSTEM 



and of its origin in the final analysis through the action 

 of an external factor does not require or depend upon 

 any particular assumptions or theories concerning 

 inheritance or evolution. Some of the critics of the 

 conception have regarded it as Lamarckian, but it is 

 not, though of course it might be used readily, if desired, 

 in a Lamarckian way. Strictly speaking, it has nothing 

 directly to do with either inheritance or evolution, 

 except in so far as it maintains that axiation or polarity, 

 and symmetry are not inherent properties or charac- 

 teristics of protoplasm. It is fundamentally a physio- 

 logical conception formulated on the basis of many 

 different lines of observational and experimental evi- 

 dence, and while its formulation in the present state of 

 our knowledge is necessarily incomplete and perhaps 

 vague, I believe a fair consideration of the evidence now 

 available justifies the conclusions advanced. 



