VARIATION AND HEREDITY 13 



called the •recessive" character. But this was not all. 

 By self-fertilizing- the tall cross-bred peas (this corre- 

 si)onds to inbreeding in animals), giants and dwarfs ap- 

 l>eared among their progeny in the average proportions 

 of 3 to 1.. 



Now when the dwarfs of this Fo generation were self- 

 fertilized, it was observed that all of their offspring 

 (F^) were dwarfs. Moreover, successive generations 

 bred from them were also all dwarfs. These are called 

 recessives, since they are "pure" as regards dwarf ness. 



But when the giants of the Fo generation were self- 

 fertilized, it was discovered that their offspring were of 

 I ICO kinds: one-third of them (pure dominants) produced 

 giants only; two-iliirds of tlicni (impure dominants) pro- 

 duced giants in the i)roportion of IJ to 1. Thus the Fo 

 generation, produced ])y allowing the crossbred forms or 

 hybrids (FJ to self-fertilize, consisted of one-cjuarter 

 pure dominants, one-half impure dominants, and one- 

 (piarter recessives. ^^ 



The law will be made clear by examining Figures 4, 5 

 and (\ in which the inheritance of the waltzing trait is 

 shown for mice, and the inheritance of colors is shown for 

 red aud white four-o 'clocks. 



FigTire 5 shows how the waltzing character is recessive 

 and absence of this character is dominant. In the first 

 generation a normal mouse (represented in black), is 

 crossed with a waltzing mouse (represented in white). 

 The result is all normal mice in the first filial (hybrid) 

 generation. When two mice of this generation are 

 crossed, they yield waltzing mice in the proportion of 

 one waltzing to three normal mice. When the waltzing 

 mice of this generation are mated, they yield waltzing 



loTlionisoii & Geddes, op. cit., p. 120. 



