Characters, Hereditary and Acquired. 47 



may be confident that at most they do so in a very faint degree ; 

 in other words, that acquired modifications are barely, if at all, 

 inherited, in the correct sense of that word '." 



So far Mr. Galton ; but for Weismann's further 

 theory of evoKition, &c., it is necessary to postulate 

 the additional doctrine in question ; and it makes 

 a literally immeasurable difference to any theory of 

 evolution whether or not we entertain this additional 

 postulate. For no matter how faintly or how fitfully 

 the substance of heredity may be modified by somatic 

 tissues, the Lamarckian principles are hypothetically 

 allowed some degree of play. And although this is 

 a lower degree than Darwin supposed, their influence 

 in determining the course of organic evolution may 

 still have been enormous ; seeing that their action in 

 any degree must always have been directive of varia- 

 tion on the one hand, and cumulative on the other. 



Thus, by merely laying this theory side by side 

 with Weismann's, we can perceive at a glance how 

 a pure theory of heredity admits of being based 

 on the postulate of Continuity alone, without cum- 

 bering itself by any further postulate as to this 

 Continuity being absolute. And this, in my opinion, 

 is the truly scientific attitude of mind for us to adopt 

 as preliminary to the following investigation. For 

 the whole investigation will be concerned — and con- 

 cerned only — with this question of Continuity as ab- 

 solute, or as admitting of degrees. There is, without 

 any question, abundant evidence to prove that the 

 substance of heredity is at least partly continuous 

 (Gemmules). It may be that there is also abundant 

 evidence to prove this substance much more largely 

 ' Theory of Heredity (Journ. Anthrop. Inst. 1875, p. 346). 



