26 The Journal of Heredity 



Columbian Male Buff Female 



SEX LINKED INHERITANCE IN BIRDS 



Figure 13. In the cross between Columbian male and Buff female, both sexes of the 

 first generation are Columbian. In the reciprocal cross this is not the case, only the 

 males are Columbian, the females being buff like their father. Further breeding experi- 

 ments prove these females to be entirely free from the Columbian color factor, and to be 

 genetically pure buffs. This type of sex-linked inheritance, found in moths, butterflies, and 

 birds, is known technically as "WZ" inheritance to distinguish it from the "XY" type of 

 inheritance found in man, and in the fruit fly, where it has been most intensively studied. 



several self-black fowls, chiefly pure 

 bred Black Orjnngtons (Fig. 12), al- 

 though a few self -blacks extracted from 

 a i)revious cross of Light Brahma by 

 White Leghorn were included. In the 

 first generation the reciprocal crosses 

 yielded dissimilar results. Columbian 

 male by black female produced all black 

 chicks (see Table 2). As adults the 

 males and females from this cross were 

 fjtiitc* similar aside frrjm secondary sex- 



ual differences in pattern.^ They were 

 black with much white lacing appear- 

 ing in the hackles, saddles, and wing 

 bows of the males (Fig. 12). These 

 males have been classified as Silver 

 Duckwings, since they resemble that 

 plumage type. The females were like- 

 wise black with white lacing on the 

 feathers of head, neck and breast, as in 

 the Birchen pattern (Fig. 12). The 

 appearance of sexual dimorphism in 



* All of the females from this cross died before the adult plumage was fully developed. 

 It is assumed that their adult pattern would have been similar to that of the black daugh- 

 ters of Fi Black $ X Columbian $ (cross 7 Table 2). 



