648 REGENERATION AND GROWTH 7 



Stages an inhibitor. Both may be organ- or even tissue-specific. They are also stage- 

 specific, and a number of extraneous agents, used experimentally, likewise show 

 a degree of stage-specificity in action. Naturally occurring external agents tend 

 to act as purely triggering stimuli, evoking a complete autogenous act of regenera- 

 tion. In this, and in other properties, for instance the increase in rate of regenera- 

 tion with increased amount being removed, regeneration shows a high degree of 

 biological adaptation. 



