COLOR INHERITANCE IN MAMMALS 



VIII, Swine — Much Evidence Still Necessary to Clear up Problems — Three 

 Independent Kinds of Variations Can Be Distinguished 



Skwall Wright 



Bureau of Animal Industry, WasJiiw^tou, D. C. 



THE luiblished data on color inheri- 

 tance in hogs are rather fragmen- 

 tary, and few certain conclusions 

 can be drawn. There are, never- 

 theless, some features of very great 

 interest. There is considerable variety 

 of color. Self colored black, red, and 

 white breeds are known. All three 

 kinds of bi-colors, and also tri -colors, are 

 familiar. The color of the wild Sus 

 scroja is none of these but a pattern 

 something like the agouti of rodents. 

 In the young there is a yellowish ground 

 color, with dark, longitudinal stripes. 

 The dark color increases later at the 

 expense of the yellow, producing a sort 

 of agouti pattern. 



WHITE PATTERNS 



There are several kinds of white 

 patterns. One of these is the belt of 

 Hampshire swine which bears a resetn- 

 blance to the pattern of Dutch belted 

 cattle, Dutch rabbits and, to a less ex- 

 tent, to that of other piebald mammals. 

 In Hampshires the ground color is black. 

 Simpson* has shown that the belt can be 



transferred to red hogs by crossing 

 Hampshire with the red Tamworths or 

 Durocs and extracting reds in later 

 generations. In this way he has devel- 

 oped a belted red breed. It is clear that, 

 whatever its mode of inheritance, the 

 factor or factors for Hampshire belt 

 belong in class lao, as determining a 

 white A^'hich replaces color irrespective of 

 its quality and producing a ipiebald 

 pattern. 



The mode of inheritance has not yet 

 been thoroughly cleared up. The pat- 

 tern varies from white merely on the 

 fore feet, through the clear-cut pattern 

 of the Hampshire in which the belt 

 passes from the forefeet over the 

 shoulders to a condition found in Ger- 

 man Hanoverian swine in which only the 

 head remains colored. There is in most 

 cases a tendency to dominance in Fi. 

 Thus in the cross of Hanoverian by the 

 self-colored European wild boar, the 

 hybrids are belted though less than in 

 Hanoverians.- Segregation of a unit 

 factor, however, is not certain. Even in 

 pure Hampshires, Spillman'^ found that 



SOLID BLACK HOG — vdEjj 



V=white belt of Hampshire. Unit factor not certain. 



EyD =white to roan, E^d =sandy to red. 



Agouti of wild vs black of Hampshire? 

 J Eg = black spots on red ground (carried by selection nearly to solid 



black in Berkshires and Poland Chinas, to solid red in Diiroc-Jersey 



and Tamworth. 



EY=solid red (present associated with D in solid white Yorkshires 



and Chesters) 



Ey, Eg and Ej, have not been proved to be triple allelomorphs. 



Two independent sets of factors may be involved. 

 2a 3 — Black of Hampshire vs Agouti of wild? (See 2ai). 



2b — 



Classification explained in paper on the mouse, Tourn.\l of Heredity, 8:373, August, 

 1917. 



1 Simpson, 0. L 1914. Jour. Her., 5:329-339. 



2 Frohhch, G. 1913. Jour. f. Landw., 61:217. 



3 Spillman, W. T- 1907. 5«., 25:541. 



ii 



