334 



The Journal of Heredity 



Yorkshire and the Red Tarn worth, 

 something of the elements that make 

 each perfect in the colors belonging to 

 its breed. And we also find that 

 Mendelism may not be condemned 

 without due analysis of contending 

 factors that may be contaminating 

 germ-cells. To make lucid I will try 

 your patience with some meditating on 

 Yorkshire and Tarn worth color-origin. 



THE YORKSHIRE WHITE. 



Yorkshire white must be treated as a 

 I^igment or coloring, the same as in the 

 paint-shop, and not as the absence of 

 something : for all white of swine known 

 to me is dominant to the darker pig- 

 ments, when crossed against them: 

 analogous to the brown, red, and gray 

 lead oxides that carbonated and further 

 oxidized produce the whitest paint. 



We would imagine the origin of the 

 White Yorkshire that has some gen- 

 ealogy, to be from the white hog of 

 China, where perhaps most of his per- 

 fection in whiteness arose before im- 

 portation by the Bakewells to England. 

 Being dominant white we can not sui> 

 pose its first exhibit to be by the meeting 

 of chromosome complements, as with 

 albinos, (the pairing of two recessive 

 chromosomes, one from each parent, 

 making the somatic exhibit in purity). 

 Nor may we guess that the first mutant 

 was of such potentiality in dominance 

 as is the single factor producing white 

 in the family of s])otted Negroes which 

 I will later mention. Analysis of this 

 Yorkshire white, which I have made by 

 hybridizing, proves the main factor only 

 to be dominant : and this the factor that 

 singly, in heterozygous pairing, w^hitens 

 every hair on the entire coat at birth, 

 but has not the power to whiten the 

 skin of the same subject. This single 

 mutant factor could have acquired its 

 I)resent jjotentiality at a single leaj), or 

 may have reached its present stage by 

 long continuous selection : we know of no 

 analysis for deciding this. A single 

 factor, by its presence or absence, says 

 white hair or colored hair, as we have 

 deduced by Mendelizing. But for the 

 perfection of white in the skin from 

 which the white hair grows, and the 

 positiveness that all the hairs shall still 



be white at maturity of the subject, 

 throughout the entire coat, we must 

 postulate the doubling, or homozygous 

 pairing, of the factor for white. We see 

 in the jack-rabbit of the plains from 

 Texas to Alberta, the progressive white- 

 ness in which every degree of duration 

 of Winter's snow adds to the perfection 

 of his invisible snow-coat. And might 

 not the white hog of China have gone 

 through the same minute, selective steps 

 of variation towards perfection, by the 

 constant desire of his Mongolian 

 breeders? That there is at least one 

 factor in the Yorkshire of high oxidizing 

 power is indicated by the fact that a 

 portion of F2 recessives of this breed and 

 of the Tamworth, are richer in tint (red), 

 and more potent in crosses, showing 

 improvement over the red of pure sub- 

 jects. Thus we find a perfection of 

 " paint making " among the extracted 

 recessive reds from the Tamworth- 

 Yorkshire cross: a few of these being 

 much more brilliant in exhibit, and 

 more potent in further Mendelizing 

 against other breeds. 



The Tamworth, now desired a bright- 

 red, is of lineal descent from the wild 

 gray Sus scrofa of Europe. We know 

 this from scattering history of his Irish 

 origin, and have greater proof from 

 hybrid analysis. It seems yet to require 

 some selecting to prevent his reversion 

 to the dark wild gray, now carried by 

 the indigenous hog of the Schwarzwald. 

 His skull-formation, though not his 

 dentition, seems good evidence also of 

 his scroja descent. While the Tam- 

 worth is termed red, there are various 

 shades and tints of this: a yellow-red 

 that fades in maturity to dirty buck- 

 skin; bright-red keeping good to old age; 

 and a ripe-cherr\'-red turning slaty- 

 black at maturity of pig. And while 

 the main factor that decides red is 

 found in all the shades, there are no 

 doubt other heritable factors shuffling 

 in or out at fonnation of the gametes, 

 sa\'ing by their j^resence or absence which 

 particular tint will be made in the coat. 



I'.\TTERN' CORREL.XTION. 



l)n)])i)ing back to the discussion of 

 outlining in color-pattern with white and 

 red, we will cite some obser\'ation : — 



