68 



The Journal of Heredity 



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number of the spots is largely deter- 

 mined by modifying factors which 

 must be numerous since no pig in F2 

 possessed as much black as a pure bred 

 Berkshire, although one had about 

 ninety-five per cent as much. Those 

 which have red color upon them as con- 

 trasted with those which have no 

 darker shade of red than sandy, consti- 

 tute almost exactly nine-sixteenths of 

 Fo and fully 100% of the backcross. 

 Therefore it is reasonably clear that the 

 Duroc-Jersey possesses two factors, 

 absent in the Berkshire, which are 

 both necessary for the production of 

 red. If we assume that either factor by 

 itself produces some shade of sandy, 

 everything is satisfactorily explained 

 except that the pigs carrying black 

 have a much higher proportion of those 

 which lack both red and sandy than do 

 the pigs which do not possess the black. 

 If we assume a factor linked to black 

 which can dilute to white the sandy 

 produced by one of the factors for red 

 when the other factor for red is absent, 

 the actual results are very close to the 

 theoretical ones. This is shown in 

 Table III. 



The author has no theory to account 

 for the presence of two shades of red on 

 the same animal. The fact that these 

 "bicolor reds" constituted almost ex- 

 actly one-fourth of the F2 generation 

 seems to point to a simple explanation, 

 but there were three easily distinguish- 

 able types of this bicolor character, as 

 follows: first, roaning, of which the 

 genetic foundation is not known; 

 second, small irregular spots of red, 

 usually around the face, particularly 

 (Ml the eyelids, while the rest of the ani- 

 mal was some lighter color; and third, 

 a lighter colored belly than sides or 

 back. This last feature is always found 

 a^ an integral part of the agouti pattern 

 where that occurs among other mam- 

 mals and seems to be connected with 

 that pattern here also, for it is very 

 prominent on the young of the wild 

 hog, and when an F.. boar which was 

 redwithasandy belly wasmatedtoan F2 

 sow (both from the Berkshire X Duroc- 

 Jersey cross), which was white but had 



