122 ARE THE EFFECTS OF USE INHERITED? 



acquired characters. This enables him to ex- 

 plain heredity by his theory of the " Continuity 

 of the Germ-plasm." 1 Parent and offspring are 

 alike successive products or offshoots of this 

 persistent germ-substance, which obviously would 

 not be correspondingly affected by modifications of 

 parts in parents, and so would render the trans- 

 mission of acquired characters impossible. 



1 Essays on Heredity, p. 104. Weismann's theory is clear, simple 

 and convenient, but incomplete ; for, unlike Darwin's theory or 

 pangenesis, it scarcely attempts any real explanation of the extremely 

 complex potentialities possessed by the reproductive elements. 

 Perhaps we might retain Darwin's self- multiplying gemmules without 

 supposing them to be thrown off by the cells, which will no longer 

 be credited with two modes of multiplication. These minute germs 

 or -gemmules may have been evolved by natural selection playing 



^^ "^ 



upon~!he sample germs that achieve development ; and they may 

 exist either separately, or (preferably but perhaps not invariably) in 

 aggregates to form Weismann's germ-plasm. 



