426 THE AMERICAN NATURALIST [Vol. LV 



(lit ion, ten males and seven females which had long ears 

 and eight males and two females with short ears. The 

 appearance of individuals of each sex in each class shows 

 that the gene must not be carried by the X chromosome. 



The First Filial Generation Inbred.— A very small 

 number of mice were obtained from inbreeding the long- 

 eared heterozygous Fj offspring. These gave, in the F2, 

 11 long to 6 short (Table IV). In a total of 17 individ- 

 uals on a one-factor basis, the numbers calculated for a 

 3:1 ratio would be 12.75 to 4.25. The results are con- 

 sistent with our previous conclusion as to the number of 

 genes involved. 



The Inbred Recessive.— The test of the inbred reces- 

 sive demonstrates that the character breeds true. Three 

 matings between short-eared males and females have 

 yielded 13 young, all with short ears (Table V). 



Conclusion 



The data given above show that the mutation " short 

 ears " wliich appears as a perfectly definite and easily 

 distiii£ruisliabl(' character in mice behaves as a recessive 

 and i< (Ifpciidrrit ii[)on a single gene which is not sex- 

 liiiked. ( >tli('r possible linkage relationships have not yet 



