212 Inheritance of Acquired Characters 



deprived of his last stronghold saw himself forced to 

 give an explanation for these co-ordinated variations 

 also, which should prove, at least from a theoretical 

 point of view, that they also might possibly be produced 

 through natural selection. But it is just in this attempted 

 explanation that he has fallen into the most evident 

 contradiction, a thing which was inevitable anyway seeing 

 that his thesis is untenable. It is worth while to spend 

 a little more time examining this contradiction. 



He utilizes for this purpose a theory which, though 

 introduced only at the last to supplement or replace the 

 earlier, already discussed theories of panmyxia and the 

 economy of the organism, was originally intended to 

 give if possible some better explanation than the earlier 

 theories offered of the continuous regression of useless 

 organs even after any further regression is of no more 

 value for natural selection. According to this theory 

 when once the involutive process has begun in a given 

 organ from any external provocation whatever, it would 

 acquire in this very way an intrinsic tendency to bring 

 about more and more retrogression. And the tendency 

 acquired by this organ and now inherent in it toward 

 constant phylogenetic regression would be accounted for 

 by the following consideration. 



Weismann affirms that when the tendency to degen- 

 erate once appears in an organ especially well developed, 

 let us suppose by natural selection, that proves that it 

 is represented from that time on in the germ plasm by 

 determinants "of smaller growing power." "But since," 

 he continues, "growth and assimilation are physiologic 

 functions, just as are contraction and secretion, so the 

 fundamental principle of intraselection is applicable to 

 them: the functional stimulus strengthens the function- 



