350 Mendel's Experiments 



equality of fertility in all plants in all generations be 

 assumed, and if, furthermore, each hybrid forms seed of 

 which one-half yields hybrids again, while the other half 

 is constant to both characters in equal proportions, the 

 ratio of numbers for the offspring in 'each generation is 

 seen by the following summary, in which A and a denote 

 again the two parental characters, and Aa the hybrid 

 forms. For brevity's sake it may be assumed that each 

 plant in each generation furnishes only 4 seeds. 



Generation A Aa a A 



1121 I 



2646 3 



3 28 28 7 



4 120 16 120 15 



5 49 6 3 2 496 3 1 

 n 2 n - i 



RATIOS 

 Aa 



2 

 2 

 2 

 2 

 2 

 2 



a 

 i 

 3 

 7 

 15 



In the tenth generation, for instance, 2 n 1 = 1023. 

 There result, therefore, in each 2,048 plants which arise in 

 this generation 1,023 with the constant dominant character, 

 1,023 with the recessive character, and only two hybrids. 



THE OFFSPRING OF HYBRIDS IN WHICH SEVERAL 

 DIFFERENTIATING CHARACTERS ARE ASSOCIATED. 



In the experiments above described plants were used 

 which differed only in one essential character*. The next 

 task consisted in ascertaining whether the law of develop- 

 ment discovered in these applied to each pair of differen- 

 tiating characters when several diverse characters are united 

 in the hybrid by crossing. As regards the form of the 

 hybrids in these cases, the experiments showed throughout 

 that this invariably more nearly approaches to that one of 

 the two parental plants which possesses the greater number 

 of dominant characters. If, for instance, the seed plant has 



* [This statement of Mendel's in the light of present knowledge is 

 open to some misconception. Though his work makes it evident that 

 such varieties may exist, it is very unlikely that Mendel could have had 

 seven pairs of varieties such that the members of each pair differed from 

 each other in only one considerable character (wesentliches Merkmal). The 

 point is probably of little theoretical or practical consequence, but a rather 

 heavy stress is thrown on " U'esentlich"} 



