326 APPENDIX 



If A be taken as denoting one of the two constant characters, for 

 instance the dominant, a, the recessive, and Aa the hybrid form in 

 which both are conjoined, the expression 



A + 1Aa + a 



shows the terms in the series for the progeny of the hybrids of two 

 differentiating characters. 



The observation made by Gartner, Kolreuter, and others, that 

 hybrids are inclined to revert to the parental forms, is also con- 

 firmed by the experiments described. It is seen that the number of 

 the hybrids which arise from one fertilisation, as compared with the 

 number of forms which become constant, and their progeny from 

 generation to generation, is continually diminishing, but that 

 nevertheless they could not entirely disappear. If an average 

 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. 



In the tenth generation, for instance, 2" — 1 = 1023. There 

 result, therefore, in each 2,084 plants which arise in this generation 

 1,023 with the constant dominant character, 1,023 with the reces- 

 sive character, and only two hybrids. 



The Offspring of Hybrids in which several Differen- 

 tiating Characters are Associated 



In the experiments above described plants were used which 

 differed only in one essential character. 1 The next task consisted 



1 [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, 



