80 



INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



That the agreement is not closer must be attributed to the fact of 

 small numbers and the premature death of many of the chicks, in conse- 

 quence of which their adult plumage colors were not fully revealed. Also, 

 many "blue" chicks produce white adults with black specks in the plumage. 



It is to be observed that this explanation calls for a special mosaic 

 (blueing) factor, but this mosaic factor brings about a blue plumage only 

 when the "white" factor is diluted, i. e., heterozygous. 



In the next generation (pen 733) I mated 2 blues together. This 

 mating is generally regarded as a unifactorial one (producing gametes 

 WM, loM) and to give in every 4 offspring 1 black, 2 blue, and 1 white. 

 I obtained the expected 50 per cent of blues, but always an excess of blacks 

 and a deficiency of whites (49 : 35 : 16, respectively). This result is doubt- 

 less due to the accident that a large proportion of the chicks were described 

 young, for it appears from my records that some blues become white when 

 older and some "blacks" are certainly blue-blacks. The deficiency of whites 

 becomes an excess of wliites in the adult stage. The whites obtained from 

 the blues are usually, but not always, splashed with black spots. 



B. SPANGLING. 



As is well known, hybrids between black fowl and White Leghorns 

 are usually white with black patches in the females, while their brothers 

 are mostly entirely white. This "spangled" condition is a heterozygous 

 one just as truly as the "blue" condition is. When a splashed hen is mated 

 to her white brother a certain proportion of the offspring are splashed again, 

 i. e., one-half of 50 per cent or 25 per cent, that being the proportion of 

 heterozygous females. Actually in 150 offspring 19.4 per cent were splashed 

 and 18.6 per cent black, while 62 per cent were recorded (largely from 

 unhatched chicks) as pure white. The splashing reappears in about the 

 expected proportion of cases. In my pen 633 I take the spangled females 

 to form gametes TVS, Ws, wS, ws, while the male seems to form gametes 

 Ws, ws; S being the spangling factor. Then [ 9 WS, Ws, wS, ws] X [c? Ws, ivs] 

 gives the combinations shown in table 65. 



Table 65. Combinations in zygotes of the second hybrid generation of the spangled strain. 



