10 



[Apr., 



gree is certainly some guide to breeding capacity. An animal 

 with a line of black ancestry is more likely to be a true-breeding 

 black than one that has a strain of red in its pedigree, but it 

 is not a sure guide. The " red " germ plasm may be carried 

 on by blacks for many generations, without coming into the 

 open in the form of a red calf. This is illustrated by the imagi- 

 nary pedigree shown in Fig. 2. The impure dominant cow in 

 Gen. I carried " red " germ cells, and the red " germ plasm 

 passes down to her daughter, grandson and great-granddaughters. 



II 



III 



* 



o 



RED 



Fi<;. 2. Illustrating ail imagiiiaiy Pedigree of Black Cattle, \\u\h repi evented 

 by Squares: Coas.s liy Circles. True -breeding Blacks represented by full black: 

 impure Dominants, carr\'ing Red, represented half Black and half White. 



No red calf appears because all of these animals, except the last, 

 have been mated with pure dominants. But at Gen. IV a new 

 bull is introduced w^hich turns out to be an im^pure dominant^ 

 though it may have had only black in its pedigree for generations. 

 If one of the great-granddaughters of the original cow is mated 

 to this bull, it will produce a red calf in Gen. V. Had the 

 breeder tested the bulls used in Gen. HI and Gen. IV by mating 

 them with red cows a proportion of red calves would have been 



