1 70 Journal of Comparative Neurology and Psychology. 



been operative at each successive evolutionary stage to deter- 

 mine the next step to be taken. 



In the doctrine of nerve components as it is now being 

 wrought out we have a concrete illustration of the correlation 

 of structural and functional data and methods in the solution of 

 some of the greater problems of vertebrate descent, and espe- 

 cially in the interpretation of the human nervous system, the 

 culmination of that evolutionary history. We shall be able to 

 present from our contributors illustrations of the practical work- 

 ings of this principle in detail within a few months. 



