HUMAN IXHERITAXCE 183 



it is not possible to recover the old ty2)e, but if two 

 races have independently arisen from the same orig- 

 inal wild type, and have accumulated different sets 

 of mutant genes, it is still possible to obtain the orig- 

 inal type by crossing in so far as each has retained 

 some of the original genes. For example, there are 

 two white breeds of fowls which when crossed pro- 

 duce offspring show^ing the colored plumage of the 

 wild jungle fowl. Similarly there are two white races 

 of sweet peas which if crossed give the color of the 

 purple Sicilian w41d pea from which our cultivated 

 forms are said to have come. Some of the races of 

 mankind have been long separated. It might seem 

 possible to recover the type from which they have 

 departed by crossing them. Racial crosses have been 

 made frequently, and the hybrids described, but 

 there is no way of determining how far the outcome 

 represents in certain respects the common ancestral 

 type, and how far it is due to the interacting domi- 

 nant factors of the combination. Possibly it might 

 be supposed that the mulatto, w4th a yellow skin, 

 that results from the white-negro cross represents 

 the type of skin color from which both white and the 

 negro races have diverged. If so, a yellow race 

 breeding true to that color might be obtained after 

 the white and the black genes had been replaced by 

 the original yellow genes. As yet there is no certain 

 record of such a consummation, although the defi- 

 ciency of white-skinned and black-skinned offspring 



