CHAPTER II. 



Later Additions to Weismann's System 

 up to the year 1892. 



I HAVE now furnished as complete a resiimS as 

 seems desirable for present purposes of Weismann's 

 theory of germ-plasm, considered both as a theory 

 of heredity and as a sequent theory of organic 

 evolution. But before proceeding to examine this 

 elaborate system as a whole, I must devote another 

 chapter to a further statement of certain later 

 additions to — and also emendations of — the system 

 as it was originally propounded. These additions 

 and alterations have reference only to the theory of 

 heredity : they do not affect the theory of organic 

 evolution as originally deduced therefrom. More- 

 over they have all been due to our more recently 

 acquired knowledge touching the morphology and 

 physiology of cell-nuclei : it is for the purpose of 

 bringing his theory of germ -plasm into accord with 

 these results of later researches that Weismann has 

 thus modified the theory as it originally stood. For 

 my own part, I do not see that very much is gained 

 by these newer additions and modifications ; but, be 

 this as it may, they are certainly very complicated, 

 and on this account I have thought it best to devote a 

 separate chapter to their consideration. Furthermore, 



