SEX-LIMITED INHERITANCE IN POULTRY 13 



the general ground color is determined almost exclusively by 

 the father's germ plasm. The shafting, likewise, is intermediate, 

 inasmuch as it is sometimes absent (though usually present 

 to an intermediate degree) in pullets from a Brown Leghorn 

 sire and is usually absent, but sometimes (as in fig. 7) shows, 

 in pullets from a Dark Brahma sire. Even though we make 

 every allowance for the circumstance that the pullets figured 

 are only about eight months old — an age at which the sharp 

 contrasts of the adults are lacking — still the conclusion can not, 

 I think, be avoided, that not all sex-dimorphic characters are 

 sex-limited. 



The Fo generation. In the spring of the following year (1911) 

 I mated together the (Brown Leghorn cf X Dark Brahma 9) 

 hybrids in Pens 1112 and 1115; and the (Dark Brahma o^ X 

 Brown Leghorn 9) hybrids were mated in Pen 1126. The 

 results from these two sets of matings are given in table 9. 



Expectation in the mating of a male Fi (Brown Leghorn cT X 

 Dark Brahma 9 ) by a female of the same origin may easily be 

 deduced by the formulae used in the earlier part of this paper. 

 Table 10 gives the formula for inheritance of lacing; W, white 

 and w, absence of white. 



This formula indicates that half of the father's sperm have 

 and half lack the W factor (inhibitor of formation of red pigment) . 

 By hypothesis only half of the eggs have the sex-chromosomes and 

 these eggs all carry absence of white (i.e. golden) hackle. Con- 

 sequently, white X golden ( = white) and no white, or red, X 

 golden ( = red) combinations for hackle color should be equally 

 common in the males; actually there are eight white hackles to 

 four red. Though the numbers are small and the accord is pro- 

 portionately not close yet the absolute departure from equality 

 is small and the result is of the expected order- — both types of 

 hackle color occur in approximately the ratio of 1 : 1. Likewise, 

 since, by hypothesis, the sex-limited characters of the pullets are 

 derived solely from the sperm there will be two sorts of pullets, 

 equally numerous, viz., white-laced and golden-laced. Actually 

 these occur in the proportions of 10 to 7. Again the proportions 

 are of the expected order. 



