DOMINANCE 



ther, one would have to secure a homozygous 

 race of fowls which formed such gametes. 



Success would be most likely to attend the 

 experiment if one selected always the sootiest 

 whites obtained from blue parents, for blue 

 results, as we have seen, from the association 

 of more black with the white and in the pat- 

 tern borne already by the white race. 



A much-debated case of inheritance which 

 involves this principle of unfixable heterozy- 

 gous characters occurs among fancy mice, in 

 the variety known as yellow. A wonderful 

 series of color varieties exists among mice 

 kept as pets, equalling or perhaps surpassing 

 that known in the case of any other mammal. 

 All these varieties appear to be derivatives 

 of the common house-mouse, with which they 

 cross readily. All are capable of explanation 

 as unit-character variations from the condition 

 of the house-mouse. Among all these varie- 

 ties yellow is most peculiar in its behavior. 

 In crosses it is dominant over all others, yet 

 is itself absolutely unfixable. 



If certain strains of yellow mice are crossed 

 with black ones, the offspring produced are of 



57 



