14 THE METHODS AND 



common expectation. But when we proceed 

 to ask how the germ-cells will be constituted 

 in the case of an individual who is cross-bred 

 in some respect, containing that is to say, an 

 ingredient from the one side of his parentage 

 and not from the other, the answer is entirely 

 contrary to all the preconceptions which either 

 science or common sense had formed about 

 heredity. For we find definite experimental 

 proof in nearly all the cases which have been 

 examined, that the germ-cells formed by such 

 individuals do either contain or not contain a 

 representation of the ingredient, just as the 

 original gametes did or did not contain it. 



[~If both parent-gametes brought a certain 

 quality in, then all the daughter gametes 

 have it ; if neither brought it in, then none 

 of the daughter gametes have it. If it came 

 in from one side and not from the other, then 

 on an average in half the resulting gametes 

 it will be present and from half it will be 



