62 Mendel's Experiments 



an average sixty-five times. The form AaBb occurs 138 

 times : it is hybrid in both characters, and behaves exactly 

 as do the hybrids from which it is derived. 



If the numbers in which the forms belonging to these 

 classes appear be compared, the ratios of 1, 2, 4 are un- 

 mistakably evident. The numbers 32, 65, 138 present very 

 fair approximations to the ratio numbers of 33, 66, 132. 



The developmental series consists, therefore, of nine 

 classes, of which four appear therein always once .and are 

 constant in both characters; the forms AB, ab, resemble 

 the parental forms, the two others present combinations 

 between the conjoined characters A, a, B, b, which com- 

 binations are likewise possibly constant. Four classes 

 appear always twice, and are constant in one character 

 and hybrid in the other. One class appears four times, 

 and is hybrid in both characters. Consequently the 

 offspring of the hybrids, if two kinds of differentiating 

 characters are combined therein, are represented by the 

 expression 



aB + ab+ZABb+ZaBb + ZAaB+ZAab 



This expression is indisputably a combination series in 

 which the two expressions for the characters A and a, B 

 and b, are combined. We arrive at the full number of the 

 classes of the series by the combination of the expres- 



sions : 



A +2 Aa+a 



B + 2 Bb + b. 

 Second Expt. 



ABC, seed parents ; abc, pollen parents ; 



A, form round ; a, form angular ; 



B, albumen yellow ; 6, albumen green ; 



C, seed-coat grey-brown, c, seed-coat white. 



