Chapter I 

 PANGENS IN THE NUCLEUS AND CYTOPLASM 



/. Introduction 



We shall now try to connect with each other the 

 conclusions to which the critical survey of previous the- 

 ories of heredity, in the first Part, and the review of the 

 present state of the cell theory, in the second Part, have 

 lead us. 



The result of the first Part was that the comparative 

 consideration of the world of organisms, from the broad- 

 est standpoint, compels us to regard specific characters as 

 being composed of innumerable, more or less independ- 

 ent factors, of which by far the most recur in various, 

 and many in extremely numerous species. The almost 

 unbounded variety of living and extinct organisms is 

 thus reduced to the numerous different combinations 

 which a comparatively small number of factors makes 

 possible. These factors are the individual hereditary 

 characters, which, indeed, most frequently, are ex- 

 tremely difficult to recognize as such in the intricate sum 

 total of the phenomena, but which, however, since every 

 one of them can vary independently from the others, 

 may, in many cases, be subjected separately to experi- 

 mental treatment. 



These hereditary characters must be grounded in liv- 

 ing matter; every vegetative germ-cell, every fertilized 

 egg-cell must potentially contain within itself all the fac- 

 tors that go to make up the characters of the respective 



