GBNBRAI, TOPICS IN INHERITANCE. ^7 



Black skin of the Silky dominates over the colorless skin of the Frizzle 

 and of the Jungle. It probably dominates throughout. 



Yellow vs. black beak and foot co/^n— Yellow of the White I^eghorn domi- 

 nates over black of the Minorca, but yellow of the Dark Brahma is domi- 

 nated by the Minorca. Here yellow behaves differently, according as it is 

 in the I^eghorn or Dark Brahma race. It is quite possible that the yellow 

 is not identical in the two groups, but that, while it is ancestral in the Dark 

 Brahma, it is secondary and a progressive character in the leghorn. The 

 lack of uniformity in dominance of yellow may be due to essential dissimi- 

 larity of the character in different races. 



White vs. dark plumage. — Aside from cases of barring and Andalusian 

 coloration, white usually dominates over dark plumage. This is true in all 

 cases where White Leghorn is employed as white race, whether the other 

 race is Game, Dark Brahma, Houdan, or Minorca. When the Silky is used 

 as the white race white is sometimes recessive (fig. 53), but it must be ac- 

 knowledged that the dark parents were not the same as were used with the 

 lycghorn, but were a Game, Frizzle, and Jungle fowl ; consequently the 

 results in the two series are not strictly comparable. However, Darwin 

 found the white of the Silky recessive to the black of the Minorca. It is 

 hardly conceivable that the white of the Silky is different from that of the 

 Leghorn ; so it must be concluded that white inherited as a solid color is 

 sometimes dominant and sometimes recessive, depending on the race in which 

 it inheres. 



Summarizing the foregoing evidence, it appears, first, that (except in 

 certain obviously complex color characters) when one of a pair of allelo- 

 morphs is dominant it is so regardless of the races crossed. This shows 

 that dominance and recessiveness depend upon a relation of the character- 

 istics per se and not upon any relation of the races into which they have 

 been introduced. This is in accord with the conclusion reached above, that 

 dominance is determined by \.)i& positive nature of the characteristic (p. 84). 



PRBPOTBNCY AND DOMINANCE. 



Prepotency was a much used and probably abused term in the period pre- 

 ceding the revival of Mendelism. In the new era all of the old terms have 

 been subjected to reexamination as to their significance. Bateson and Saun- 

 ders ( 1 902, p. 121) use the term ' ' as signifying determination of dominance, ' ' 

 i. e., whether the normally dominant or the normally recessive character 

 shall be in any case actually dominant. Castle (1905, pp. 58-64) shows that 

 although rough coat is dominant over smooth coat, a few smooth-coated, 

 mothers will, when crossed with rough males, produce partial-rough young. 

 The normally recessive character here partially dominates. In my own 

 experiments the most remarkable case of dominance is exhibited by a gamete 

 from the maternal side that produced the Houdan x White Leghorn hybrid 



