go Heredity and Eugenics 



chemistry whether or not an atom is a reality, for the 

 law of "Definite and Multiple Proportions" upon which 

 analytical chemistry is based is still valid. In the same 

 way, it makes no difference whether one regards unit- 

 characters as actual units and their segregation as com- 

 plete, or whether one sees in organisms a mutual dependence 

 between characters and a quantitative or partial segrega- 

 tion among gametic factors, the notation is useful either 

 way to make clear the facts of heredity as shown by actual 

 experiment. 



In a simple case such as that which has just been con- 

 sidered (segregation of starchy and non-starchy seeds), the 

 mathematical reasoning that led Mendel to his conclusions 

 can be shown to be correct. In dealing with some 30,000 

 progeny, I have found ^that in the F 2 generation there 

 were 23,529 starchy and 7,811 non-starchy seeds, a ratio of 

 3.0031 : 0.9969=1= .0066. This is a 3 : i ratio well within 

 the probable error. Furthermore, I find that the positive 

 and negative departures from the 3 : i ratio that occur in 

 individual ears, are exactly what should be expected by the 

 mathematical theory of error. 



In more complicated cases, sometimes there are depar- 

 tures from the ratio expected normally that can hardly be 

 explained by the theory of error, yet hi such cases one is 

 warranted in assuming that misunderstood complications 

 either obscure or modify the action of Mendel's law. 



Since such accurate ratios as that given above cannot 

 be expected except by absolute division of the gametes into 

 two kinds equal in number, it is difficult to believe that 

 there is not real, exact, and complete segregation. This 

 would be the inevitable conclusion but for the fact that 

 extracted pure types do not always breed true as they 



