OUR FUTURE COURSE 213 



and differentiation. The potentialities of the whole 

 organism must be present in the fertilized ovum, 

 yet they are realized only through gradual de- 

 velopment, with a gradual change of internal 

 environmental relations. Given a normal oppor- 

 tunity, they express their inherent qualities nor- 

 mally in the adult, but the very nature of their 

 attainment of this degree of expression suggests 

 the possibility of some fluctuation in their later 

 functional capacities, of later emergents. 



If change through use and disuse may thus 

 affect the chromosomes of the germ cells, the con- 

 clusion does not follow that the next generation 

 will show the same character as its parents. It 

 must still encounter the stimulus which brought 

 out that character previously. If the stimulus is 

 present, or better still, if it is intensified, there is a 

 possibility that the condition of the genes may 

 reach another degree of development, and so, gen- 

 eration after generation, lead to a state which was 

 beyond the immediate possibilities of their pro- 

 genitors. But if the stimulus is lacking, the pos- 

 sibility still exists that the heritage may respond 

 as in previous generations. 



During the entire period of development of a 

 character in this manner it must maintain a place 

 in the organism as a whole. If the organism exists 

 in a given condition, then the maintenance of each 

 part must conform to that condition, and if one 



