i8o THE POPULAR SCIENCE MONTHLY. 



must be enormously increased with the development of every 

 species. A new principle must therefore be found to explain the 

 observed fact. Strangely enough, he finds this principle to be 

 none other than the Lamarckian law of the effect of external con- 

 ditions in modifying the hereditary elements ! 



" Amphimixis alone could never produce a multiplication of 

 the determinants. The cause of hereditary variation must lie 

 deeper than this; it must be due to the direct effect of external in- 

 fluences on the biophors and determinants." * 



It is easy to see that this is a complete abandonment of his 

 fundamental doctrine of the immutability of the germ-plasm, and 

 here again he shifts the point of the argument to the quantitative* 

 and would have us believe that it was the same thing to say that 

 it possesses " great power of remaining constant." But he adds : 



" We can none the less avoid assuming that the elements of the 

 germ-plasm i.e., the biophors and determinants are subject to 

 continual changes of composition during their almost uninter- 

 rupted growth, and that these very minute fluctuations, which are 

 imperceptible to us, are the primary cause of the greater deviations 

 in the determinants, which we finally observe in the form of indi- 

 vidual variations." \ 



These variations that take place in the hereditary elements he 

 ascribes to " the impossibility of a complete uniformity as regards 

 nutrition existing during growth," or to " the modifying influence 

 of nutrition." The following passage is as complete an admission 

 of the Lamarckian principle as any one need wish, while at the 

 same time it illustrates over again his characteristic tendency to 

 evade the issue by maintaining that its influence is small com- 

 pared to that of some other principle : 



" Even though it can no longer be doubted that climatic and 

 other external influences are capable of producing permanent 

 variations in a species, owing to the fact that, after acting uni- 

 formly for a long period, they cause the first slight modifications 

 of certain determinants to increase, and gradually affect the less 

 changeable variants of the determinants also, the countless ma- 

 jority of modifications is not due to this cause, but to the processes 

 of selection." J 



In this passage there is a curious psychological implication in 

 the expresssion " no longer," which obviously refers to the changes 

 in his own mind, that are by him projected to the world at large, 

 which, as a matter of fact, has from the first intuitively arrived 

 at the conclusion which has cost him such a great cycle of elab- 

 orate reasoning. This new theory of his as to the origin of varia- 

 tions is summed up in the following paragraph : 



* The Germ-Plasm, p. 415. \ Ibid., p. 417. \ Ibid., p. 422. 



