OUR FUTURE COURSE 209 



mental conditions, whether or not the results are 

 adaptive. 



The chief limitation of this theory is the old 

 difficulty of associating the responses of somatic 

 structures with the germ cells. Since the struc- 

 tures involved in the development of acquired 

 characters are somatic, the chromosomes directly 

 associated with the response are necessarily so- 

 matic. The possibility of a change in the functional 

 capacity of the chromosomes as an organism re- 

 sponds to environmental stimuli is a distinctly 

 valuable factor in evolutionary theory, but it does 

 not solve the problem of associating these changes 

 with the chromosomes which are handed down to 

 succeeding generations. 



Weismann's interpretation of the continuity of 

 the germ plasm has had a most unfortunate influ- 

 ence on scientific consideration of this problem. 

 The continuity which he emphasized exists; in- 

 deed, it is so logical and in some cases has been so 

 clearly demonstrated that it stands out as one of 

 the salient facts of heredity. But the fact of ger- 

 minal continuity is a wholly different thing from the 

 isolation and insulation of germ plasm which Weis- 

 mann proposed. We may even admit the validity 

 for certain purposes of his distinction between 

 germ plasm and somatoplasm without attaining the 

 position which he defended. Although we are still 

 ignorant of any mechanism whereby the influences 



