DI-HYBRID CROSSES 175 



itself in the visible character of the grain produced 

 from it. 

 The following result was actually obtained in this 



way : 



Smooth yellow grains 2,869, or 25-3 per cent. 

 Smooth white grains 2,933, or 257 

 Wrinkled yellow grains 2,798, or 24*5 

 Wrinkled white grains 2,803, or 24*5 



Thus we see that a nearly equal number of the germ 

 cells of the double heterozygote bears each of the four 

 possible combinations of characters that is to say, it 

 is an even chance whether a particular gamete, which 

 bears the allelomorph yellowness, bears also smoothness 

 or wrinkledness. In other words, the two pairs of 

 allelomorphs segregate in entire independence the one 

 of the other. It is particularly to be noticed that we 

 arrive in this way at two perfectly new combinations 

 of characters, which were not shown by the original 

 parent strains. We have synthesized two new sorts 

 of maize with smooth white and wrinkled yellow grains 

 respectively. In a precisely similar way, if the cross 

 is made between strains of which the grains are re- 

 spectively smooth white and wrinkled yellow, we 

 should obtain in F 2 the new combinations smooth 

 yellow and wrinkled white. 



The result obtained on self-fertilizing the hybrid 

 plant is somewhat more complicated. 



If we write A for yellowness, a for whiteness, B for 

 smoothness, and b for wrinkledness as before, AB x ab 

 gives the heterozygote A Bab. Equal numbers of the 

 germ cells of the heterozygote will be of the composi- 

 tions AB, Ab, aB, and ab. 



