Dunn : Color Inheritance In Fowls 



31 



served with as little black in these 

 parts as the original buff parents. 

 None was found outside the range of 

 darkness of pure Columbian fowls. 

 The cross with black cannot be said, 

 therefore, to have had any darkening 

 effect on the Columbian ])attern. 



Among the extended offspring there 

 was considerable variation in the 

 amount of black in the plumage, al- 

 though there was no overlapping be- 

 tween the extended and restricted 

 classes. The colors found diluting 

 black, or appearing in a pattern on a 

 black ground were either silver (white) 

 or buff' (Fig. 13, bottom row), al- 

 though in some cases, particularlv 

 among the males, it was very hard to 

 tell whether the extra color was white 

 or buff. These doubtful cases were 

 birds with extremely light straw or 

 cream markings which were contin- 

 uously variable with the pure white 

 and buff' marked classes. No self 

 (unmarked) blacks were recovered. 

 Such birds were expected from 

 crosses 3. 4, 5 and 8. The fact that 

 no fowls hatched from the backcross 

 with Columbian or with buff would be 

 pure for extension (E'^E'^) might be 

 expected to account for the absence of 

 pure black segregates were it not for 

 the fact that the females from cross 6 

 Columbian $ X Black S ) are known 

 to have been heterozygous in exten- 

 sion (E'^e^s — ) and yet to have de- 

 veloped self black plumage. The 

 paucity of numbers or the contribu- 

 tion of pattern factors by the later 

 buffs and Columbians used may ac- 

 count for the non-appearance of 

 blacks. The present evidence is not 

 critical. 



The patterns in which the white or 

 buff pigments appeared on the black 

 ground-color of the extended back- 

 cross female chicks were various, al- 

 though most of them could be referred 

 to the general class of penciling as it 

 appears in the Partridge or Dark 

 Brahma pattern, concentric lines of 

 light color on a daik ground, follow- 

 ing roughly the contour of the feather. 

 In pattern the females varied from the 



Birchen type with light color only on 

 the head, neck and upper breast (Fig. 

 12) to a light Dark Brahma or Part- 

 ridge type. In the males the light pig- 

 ments appeared principally on the 

 feathers of the hackle, saddle, and 

 wing bow, either as lacing, or as a 

 color occupying the whole feather. 



Most of the males could be classified 

 as Silver or Buff Duckwings. Here, 

 as in the females, there was evidence 

 of considerable variation in the 

 amount of black pigment present in 

 the body feathers, and it appeared 

 that in addition to a main factor gov- 

 erning the extension of black to all 

 parts there were minor factors regu- 

 lating the depth of saturation of the 

 black pigment. In the juvenile plum- 

 age some males showed evidences of 

 the female type of penciling. This 

 was never present in adult male plum- 

 age with the exception of the mark- 

 ings on the breast feathers of some 

 very light males. The Duckwing pat- 

 tern is the male equivalent of the 

 partridge or penciled pattern in the 

 female and appears in the males of 

 such varieties as the Dark Brahma or 

 Partridge Plymouth Rocks. The ab- 

 sence of pencilling in the males prob- 

 ably constitutes a secondary sexual or 

 sex-limited difference, dependent on 

 the presence of testicular hormone or 

 the absence of an ovarian secretion. 

 Some of the backcross Duckwing 

 males might, therefore, be expected to 

 transmit pencilling. No progeny tests 

 or castration experiments have yet 

 been completed as a test of this sup- 

 position. 



Concerning the source of the pencil- 

 ing which appeared in the backcross 

 females we have no exact information. 

 It may have been present in the black 

 parents, which lacked the buff or sil- 

 ver pigment needed to fill the pattern ; 

 or as is more probable it may have been 

 present in the Columbian parent, but 

 unable to express itself in the absence 

 of the extension factor. Light Brahma 

 (Columbian) fowls are sometimes seen 

 which have more than the usual 

 amount of black pigment in the under- 



