LINE BREEDING AND MENDEL'S LAW 193 



much to do with modifying results. Should we cross 

 the black and the white bantams, the resulting progeny 

 would be, as to appearance, all black. In this, black is 

 said to be dominant over white white is spoken of as 

 recessive ; since it disappears in the first generation of 

 the progeny. But lo ! if we breed birds of this first 

 generation together, this recessive reappears in a cer- 

 tain fairly fixed proportion of about 25 per cent. These 

 white birds will thenceforward breed only white stock. 

 The 75 per cent of blacks, however, are of two kinds as 

 to tendency ; they behave differently. These are dis- 

 tinguished as (a) "pure dominants," and (^) "impure 

 dominants." The pure dominants give only blacks 

 thenceforward, even when mated with white birds. The 

 impure dominants, like their parents, give three blacks 

 to one white, in the progeny. 



It is explained that the two germs which unite (the 

 male and the female germ) to form any new individual, 

 are transmitted as entities or units, and not as a com- 

 bination. That is, no germ cell can carry both black 

 and white ; it must be either " a black germ " or " a 

 white germ," as one may say. If both the meeting 

 germs which unite to form the new individual are 

 " white," nothing but white can be produced. If both 

 are "black," nothing but pure blacks can be produced. 

 In effect, the father and mother cells are then pure 

 blacks and give only blacks. If there are an equal num- 

 ber of each color produced by each parent, the above 

 accounts for all unions of the same kind of germ cells. 

 But what would you expect, if the black of the male 

 chanced to meet the white of the female ? Would you 

 say gray ? Not so Nature. Since they are transmitted, 



