178 MENDELISM 



One pure, aBaB, breeding true to the (new) 

 smooth white type. 



Two aBab, giving both smooth white and 

 wrinkled white. 



The remaining individual is ab in appearance and 

 abab in constitution, and breeds true to the wrinkled 

 white type. 



The expected behaviour of all these different types 

 can be followed out by the aid of suitable breeding 

 experiments, and not only has this been done in the 

 case of the cross which we have been considering, but 

 precisely similar phenomena have been shown to be 

 taking place in a large number of other characters in 

 many different species of plants and in a good many 

 animals as well. 



We are now in a position to state the important 

 proposition known as Mendel's law, which is to the 

 following effect : 



The gametes of a heterozygote bear the pure parental 

 allelomorphs completely separated from one another, 

 and the numerical distribution of the separate allelo- 

 morphs in the gametes is such that all possible com- 

 binations of them are present in approximately equal 

 numbers. (Note that it is impossible for both members 

 of the same pair of allelomorphs to occur together in 

 the same gamete.) 



This is the essence of the great discovery made by 

 Gregor Mendel, Abbot of Brunn, and published by 

 him in the Transactions of the Brunn Natural History 

 Society in 1866. By some extraordinary chance 

 Mendel's paper was entirely lost sight of until the 



