MENDELISM 121 



other green seeds (it does not matter which forms the male 

 and which the female of the parent generation P), their 

 hybrid offspring (called the first filial generation FJ will all 

 yield pods with yellow seeds. That is, yellow is " domi- 

 nant " over green. When these yellow peas (F x ) are inbred 

 among themselves, yellow and green peas appear once more 

 in the second hybrid generation (F 2 ) in a definite pro- 

 portion viz., three yellows to one green showing thereby 

 that the individuals of the F x generation were not pure 

 yellows, but that in some of them green was latent, or, as 

 Mendel termed it, green is " recessive/' Now, on further 

 inbreeding of the green and yellow peas of the F 2 generation, 

 each kind separately, it is found that the green peas breed 

 true, producing only green peas again for any indefinite 

 number of generations. But the yellow peas of the F 2 

 generation, when inbred, are of two kinds one part again 

 produces only yellow peas, breeding true throughout all 

 successive generations, while the remaining two parts of 

 them produce yellow and green peas, again in the pro- 

 portion of three yellows to one green. This third filial 

 generation (F 3 ), when further inbred (each kind separately), 

 in a similar way repeats the same phenomenon : the green 

 breed true, while the yellow once more can be divided 

 into one part of true breeding yellows and two parts of 

 impure yellows, which again yield yellow and green, and 

 so on. 



If we denote the yellow dominant parent by D, and the 

 green recessive parent by R, we get a hybrid offspring F x , 

 which can be denoted by D(R), R being in brackets to 

 show that it is recessive to D. The hybrid D(R), being in 

 appearance like D, gives, when inbred, 3D + iR. But the 

 3 D, when propagated, show that they can be separated 

 into i D + 2 D(R), D being pure dominants, while the 



2 D(R) once more, when inbred, can be differentiated into 



3 D + 1 R, etc. 



We get, accordingly, the following scheme of Mendelian 

 inheritance : 



16 



