THE INHERITED IMPULSE. 141 



generation. Mr. Francis Gallon has described 

 some wonderful cases where diseases which were 

 hereditary appeared earlier by a great many years 

 in the children, and also still earlier in the grand- 

 children. 



This general principle has been summed up by 

 Professor Weismann as follows : — 



" The line of direction of development is essen- 

 tially the following : — 



" I. The development commences with a state 

 of simplicity and advances gradually to one of 

 complexity. 



" 2. New characteristics first make their appear- 

 ance in the last stage of the ontogeny. 



" 3. Such characters then become gradually carried 

 back to the earlier ontogenetic stages, thus displac- 

 ing the older characters until the latter disappear 

 completely." ^ 



We come now to consider the important part 

 played by nervous association. Since growth and 

 all the customary responses to stimuli of the environ- 

 ment are carried on only through the mediation 

 of nervous forces, it follows that these responses 

 will be subject to the laws of nervous phenomena. 

 We have already seen that we must regard living 

 matter as something that is constantly repeating 



^ Weismann, -Studies in the Theory of Descent, Vol. I., p. 274. 



