OUR FUTURE COURSE 225 



established, and with scarcely less certainty we 

 may say that the germinal chromosomes are 

 affected. There is, however, no more reason to 

 suppose that the condition will persist after a few 

 generations if the inciting stimulus is removed 

 than to conclude a ^priori that such a cumulative 

 change may not occur. If cumulative change does 

 not take place, then studies of individual response 

 are not likely to have value in evolution, but the 

 available experimental evidence does not point 

 to this end. 



Given a cumulative response of considerable 

 degree, it is desirable next to build it up to a maxi- 

 mum. It is conceivable that the degree of develop- 

 ment attained may become a factor of such im- 

 portance in the internal environment that internal 

 coordination may, after a time, guarantee its per- 

 petuation. The factor of time appears to be 

 important here, and may be an insurmountable 

 obstacle for experimentation if we can judge by 

 the long geological periods which have been oc- 

 cupied by the evolution of known species. There 

 is, however, no reason to rulq this possibility out; 

 directly adaptive responses must be inherited in 

 this way, if at all. Such a result would be the 

 inheritance of acquired characters in a very simple 

 form. 



It is more probable that the factor of usefulness 

 in relation to other than the inciting stimuli may 



