THE INHERITED IMPULSE. 139 



That is, when each repetition was completed, its ef- 

 fects would be equal to a new element in the result 

 produced by the action of the environment on the 

 organism. Thus all generations, from the first to the 

 last, must begin alike, and start alike on the same 

 course of growth, but each repetition adds something 

 to each generation not possessed by the preceding 

 generation, until the full-grown of the ten-thousandth 

 generation may differ vastly from the adult of the 

 first generation. We see here the explanation of the 

 greatest general law of embryology, — that each indi- 

 vidual, in its development from inception to maturity, 

 repeats the history of the evolution of its race. 



This added complexity in each generation may 

 at first thought seem inadequate to account for 

 such great consequences. But we must remember 

 that this repetition is constantly strengthening and 

 co-ordinating those nervous elements which control 

 the entire growth and development, and which, 

 above all things, chiefly receive and transmit the 

 influence of the formative forces of the environ- 

 ment. 



This principle which I have endeavoured to set 

 forth here explains a number of well-known facts. 

 Since each generation begins its life by responding 

 to the customary stimuli that caused the growth 

 of all its ancestors, and, when it has finished that 



