PHENOMENA OF INHERITANCE 253 



criticism on the part of some biologists of the 

 principle of unit characters. It is said that 

 unit characters cannot be independent and dis- 

 crete things ; the organism itself is a unity and 

 every one of its parts, every one of its charac- 

 ters, must influence more or less every other 

 part and every other character. Certainly unit 

 characters cannot be absolutely independent of 

 one another; the various parts and organs of 

 the body, and even the organism as a whole, 

 are not absolutely independent, and yet there 

 are varying degrees of independence in organ- 

 isms, organs, cells, parts of cells, hereditary 

 units and characters which make it possible for 

 purposes of analysis to deal with these things 

 as if they were really independent though we 

 know they are not. 



Of course characters of adult individuals do 

 not exist as such in germ cells, but there is no 

 escape from the conclusion that in the case of 

 inherited differences between mature organ- 

 isms there must have been differences in the 

 constitution of the germ cells from which they 

 developed. For every inherited character 

 there must have been a germinal cause in the 



