436 Pork Production 



So-called reversions ^ are hereditary variations and may 

 be defined as the reappearance of a character in an indi-- 

 vidual which was not present or shown in its immediate 

 ancestry, but which was present in two or more of the 

 individuals farther back. It is the "cropping up" of a 

 character which has been "lost" for several generations. 

 The appearance of spotted pigs among Poland-Chinas 

 bred according to the medium or old-type standard is a 

 good instance of reverting back to the old type, or the oc- 

 casional appearance of spots of red hair among Berkshires. 

 The common tendency of so-called big-type parents to 

 throw pigs of the small fine-boned type is another instance 

 of the same tendency. 



In Plate XII is shown a white sow with a litter of pigs 

 containing one black one, a reversion.^ The sire of these 

 pigs was white like the dam, but both were cross-bred, the 

 product of mating a Berkshire and Yorkshire. In this 

 case the black color skipped but one generation. In 

 Fig. 18 the principle of all variations of this kind is 

 illustrated. 



This diagram supposes a Yorkshire and Berkshire to be 

 mated. All the pigs from this first cross will be white like 

 the Yorkshire parent, as proved by actual tests. These 

 cross-bred white pigs are then mated to a pure Yorkshire 

 boar and again all the pigs are white. If these white pigs, 

 which in breeding are said to be three-fourths Yorkshire 

 and one-fourth Berkshire, are mated to a boar of the same 

 breeding, as illustrated in the diagram, the chances are 

 that some of the pigs will.be black. In this case there is 

 a "cropping out" of a character which was not present in 



' Sometimes called atavism. So-called " sports " are usually 

 reversions. 



* W. W. Smith: American Breeders' Magazine, p. 116. 



