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THE AMERICAN NATURALIST [Vol. XLIV 



anism exists whereby the germ-cells may be so influenced 

 as to bring about the parallel modification of parent and 

 offspring, such a mechanism would be of exactly the same 

 value for evolution as the ct inheritance of acquired char- 

 acters" hi the old sense. For heredity, however, the 

 case would be different. We should still be able to go 

 on talking about the "continuity of the germ-plasm," 

 though that expression would have been shorn of much 

 of its meaning. 



7. Finally, we have the view that the changes under- 

 gone by the parent body are in some way registered in 

 the germ-cells, so as to be repeated, in a certain measure, 

 in the body of the offspring. The ' ' classical ' ' attempt to 

 make this process intelligible is of course Darwin's hy- 

 pothesis of "pangenesis." Other views have been put 

 forward recently 17 which are scarcely to be distinguished 

 from the preceding type of explanation (no. 6). 



It would not be profitable to enter into any scholastic 

 discussion of these various hypotheses. One after an- 

 other of these alternatives must be excluded by carefully 

 planned experiments ; and it is the intention of the present 

 writer to continue such experiments on a much greater 

 scale in the near future. 



November 6, 1909. 

 17 E. g., by Cunningham, Archiv fur Entwicklungsmechanik, 1908. 



