VITAL RESERVES 315 



behavior pattern. And this local activation or rein- 

 forcement is never lost or diminished, though in adult 

 \Uq its character may be greatly changed and it may 

 come under the influence of other regions of more 

 powerful and effective control. 



Tracy has shown that in these fish the first move- 

 ments are strictly local endogenous or ''spontaneous" 

 activities of the separate parts of the body. These 

 parts are successively connected by developing nerv- 

 ous pathways with resulting integration of the dis- 

 persed activities into unified reflex patterns. This is 

 well advanced before the larva is capable of making 

 any response whatever to external stimulation. As de- 

 velopment proceeds, the exteroceptive reactions are 

 built upon the foundation already laid down in the 

 endogenous behavior patterns. The externally ex- 

 cited or exogenous nervous impulses "capture'* and 

 bridle the more primitive endogenous motor systems, 

 which 



form a continuous ontogenetic series with the voluntary move- 

 ments of the adult It is suggested that voluntary move- 

 ments are the result of the organismic integration of the endo- 

 genous activity of the various mechanisms (visceral and associa- 

 tional) of which the organism is composed through the estabUsh- 

 ment of an excitation gradient in the central nervous system 

 which enables impulses from some one mechanism to obtain 

 temporary possession of the final common path to the exclusion 

 of all others. 



Cortical evolution seems to be the culminating 

 phase of the process here sketched, whose earliest 



