12 



315 round and yellow, 

 101 wrinkled and yellow, 

 108 round and green, 

 32 wrinkled and green. 



All were sown the following year. 

 Eleven of the round yellow seeds did 

 not yield plants, and three plants did 

 not form seeds. Among the rest: 



38 had round yellow seeds AB 



65 round yellow and green seeds ABb 

 60 round yellow and wrinkled 



yellow seeds AaB 



138 round yellow and green, 

 wrinkled yellow and green 

 seeds AaBb 



From the wrinkled yellow seeds 96 re- 

 sulting plants bore seed, of which: 



28 had only wrinkled yellow seeds aB 

 68 wrinkled yellow and green seeds aBb. 



From 108 round green seeds 102 re- 

 sulting plants fruited, of which: 



35 had only round green seeds Ab 



67 round and wrinkled green seeds Aab. 



The wrinkled green seeds yielded 30 

 plants which bore seeds all of like char- 

 acter; they remained constant ab. 



The offspring of the hybrids ap- 

 peared therefore under nine different 

 forms, some of them in very unequal 

 numbers. When these are collected and 

 co-ordinated we find: 



The whole of the forms may be 

 classed into three essentially different 

 groups. The first includes those with 

 the signs AB, Ab, aB, and ab: they 



MENDEL 



possess only constant characters and 

 do not vary again in the next genera- 

 tion. Each of these forms is represented 

 on the average thirty-three times. The 

 second group includes the signs ABb, 

 aBb, AaB, Aab: these are constant in 

 one character and hybrid in another, 

 and vary in the next generation only as 

 regards the hybrid-character. Each of 

 these appears on 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 33, 

 65, 138 present very fair approxima- 

 tions 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 other present combina- 

 tions between the conjoined characters 

 A, a, B, b, which combinations 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. Con- 

 sequently the offspring of the hybrids, 

 if two kinds of differentiating char- 

 acters are combined therein, are repre- 

 sented by the expression 



AB + Ab + ^B + ab + 2ABb 

 +• laBb + lAaB + 2 Aab + ^AaBb. 



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 ex- 

 pressions: 



