GROWTH AND REPRODUCTION 57 



educative stimuli. Through the bonding together 

 or association of many engrams it becomes possible 

 for the higher animal to execute very complex series 

 of actions as, for example, when a trained musi- 

 cian renders an elaborate composition from memory 

 and without taking cognizance of individual keys, 

 that is, with little intrusion upon the automatism 

 established by long habit. 



There is good evidence to show that the effects 

 of external stimulation are not confined to those 

 subtle changes, still indefinable in terms of chemical 

 and physical processes, which are the basis of the 

 engrams of habit, association, memory, and thought. 

 The changes attributable to stimulation clearly 

 extend to definite morphological changes, but we 

 cannot yet say whether the delicate traces of memory 

 are expressed in the more refined kinds of morpho- 

 logical alterations of protoplasm which are possibly 

 recognizable by known methods of study. The 

 degree in which the development of the individual 

 that is, the ontologenetic development is con- 

 trollable by the variation of external stimuli is in a 

 high degree surprising. By altering the conditions 

 of cultivation the color of the flower Campanula 

 trachelium can be changed from blue to white and 

 back again from white to blue, and Klebs has suc- 

 ceeded in bringing about the experimental formation 

 of apetalous flowers with one instead of two rows 

 of stamens. 



Now the mnemic theory of heredity assumes that 



