Jan. i 5 , 1921 Inheritance of Syndactylism and Color in Swine 603 



accuracy of classification. The fact that yellow may give red, yellow, 

 and cream and that the cream-colored may give red, yellow, and cream 

 leads us to believe that there is an interaction of factors producing 

 intensity of red and that similar somatic creams are not necessarily of the 

 same genetic constitution. The case appears much like the belt in the 

 Hampshire, where either belted X belted or nonbelted X nonbelted may 

 give both forms; or like purple and white aleurone in maize, where either 

 white X white or purple X purple may give both forms. We may add 

 that the adult creams can hardly be distinguished from Chester White 

 or Yorkshire color. Under the microscope these creams show little or no 

 pigment in the cortex of the hair but show yellow granules in the medulla. 

 Some white hairs from the Berkshire and Chester White may also show 

 yellow pigment. We have seen white hairs from the Berkshire which 

 show yellow pigment in the medulla exactly like our creams. 



The fact that red hair may be so diluted as to be almost if not quite 

 indistinguishable from white hair suggests that the so-called white hair 

 in some breeds may really be a very dilute red. Severson's experiments 

 (8) show that Berkshire mated to Duroc-Jersey may give white and 

 black spotted rather than the usual red or yellow and black. If the 

 white hair of the Berkshire is really a dilute red, such a result would be 

 expected in occasional matings of Berkshire to Duroc-Jerseys carrying 

 recessive diluters; and there seems to be much evidence that Duroc- 

 Jerseys carry recessive dilution factors, for much lighter animals than the 

 standards require are known. Severson mated such a white and black 

 hybrid back to a Berkshire and obtained some red and black offspring. 

 Disregarding the black, this mating is like our matings of two creams 

 which gave reds, and it thus adds weight to our hypothesis that the 

 intenser shades, like red and yellow, are due to interaction of at least 

 two pairs of independent factors; but the more dilute shades, like cream 

 or white, are due to the absence of one or both interacting factors. That 

 is, zygotes with both interacting factors A and B would be red or yellow, 

 while zygotes with either A or B, or neither, would be cream or white. 

 The fact that creams or whites form one distinct grade and yellow and 

 red form another leads us to believe that the two groups are quite distinct. 

 The slight variations in red and yellow or in the creams may be due to 

 other minor factors. Summarizing, we may say that there are three 

 sources of evidence which indicate that cream or white may be dilute red, 

 that dilution and intensity are complex characters due to interaction of 

 independent factors, and that the so-called white hair in some breeds is 

 really a cream or very dilute red, as follows: (1) Yellow pigment was 

 found in the medulla of the hair of our creams and in the white hair of 

 Berkshires, (2) red offspring were derived from our creams mated inter se, 

 and (3) red and black spotted offspring were derived from Severson's 

 white and black spotted hybrid (from Duroc Jersey X Berkshire) 

 mated to Berkshire. 



