74 HEREDITY AND ENVIRONMENT 



same sense that the elements of the other 

 psychic processes or of the organs of the body 

 are there present; not as a miniature of the 

 adult condition, but rather in the form of ele- 

 ments or factors, which by a long series of 

 combinations and transformations, due to in- 

 teractions with one another and with the en- 

 vironment, give rise to the fully developed 

 condition. 



Finally there seems good reason for believ- 

 ing that the continuity of consciousness, the 

 continuing sense of identity, is associated with 

 the continuity of material substance, for in 

 spite of frequent changes of the materials of 

 which we are composed our sense of identity 

 remains undisturbed. However, the contin- 

 uity of protoplasmic and cellular organization 

 generally remains undisturbed throughout life, 

 and the continuity of consciousness is asso- 

 ciated with this continuity of organization, 

 especially in certain parts of the brain. It is 

 an interesting fact that in man, and in several 

 other animals which may be assumed to have 

 a sense of identity, the nerve cells, especially 

 those of the brain, cease dividing at an early 



