94 Missouri Agricultural Report. 



a heterozygote by selection, and we now know why this is the case. 

 It is because of the law of separation of character pairs when 

 reproductive cells are formed. How, then, shall the breeder of 

 plants and animals secure any advantage from this law? 



LAW OF RECOMBINATION. 



We come now to a third law which is immensely more im- 

 portant than either of the two already considered ; but since it is, 

 in part, a direct consequence of the second law it has not usually 

 received separate treatment by writers on this subject. This third 

 law is the law of recombination. It may be stated as follows : In 

 the offspring of a hybrid there will be found every possible com- 

 bination of the characters of the original parents of the hybrids. 

 This presupposes, of course, that the progeny are numerous enough 

 to permit each of these combinations to occur. 



For example, Hereford cattle are horned and have white faces. 

 Polled Durham cattle have colored faces and are hornless. If we 

 cross these two breeds, the calves inherit both white face and red 

 face, both horns and no horns. Because of the law of dominance 

 the crossbred calves will exhibit white faces, and they will also be 

 polled, i. e., hornless. 



Figure 4.— PROGENY OF HEREFORD POLL DURHAM CROSS. 



1. Colored face and horns. 



2. Colored face and poll character. 

 ; 3. White face and horns. 



4. White face and poll character. 



Now the calves of these crossbreds will present every possible 

 combination of these characters. (Fig. 4.) For instance, some 

 vAW have colored face, with horns ; some colored face, without 

 horns; others have white face and horns, while still others have 

 white face without horns. It will be noticed that type 2 is like 

 the original Polled Durham parent, while type 3 is like the Here- 

 ford. But types 1 and 4 are entirely new. Type 4 has all the 

 marks of a pure Hereford except that it has no horns. 



The importance of such a case as we are considering is easily 

 seen when we remember that horns on cattle are worse than useless 

 ornaments. Buyers at the great cattle marts pay half a cent a 

 pound more for hornless beef cattle than they will for horned, for 

 they know that a carload of horned steers will show many bruises 

 that injure the meat. 



Many breeders of Shorthorn cattle long ago recognized the 



