194 



Bulletin No. 155. — 1913. 



the white and in the barred birds. But the ratios have an approxi- 

 mate agreement and the sex-ratios are all in the expected sense. In 

 Table 15, showing the F2 results of the 1913 series, it appears that 

 the experimental results come very close to the expected. 



Case 3b. — {White Leghorn X Black Minorca) d^ X Black Min- 

 orca 9. (Table 10, p. 174). It has been shown in Table 10 that 

 when the White Leghorn X Black Minorca Fi d^ was bred back to 

 pure Black Minorca 99, the offspring included white, black and 

 barred birds. We may now submit this case to Mendelian analysis, 

 making use of the same factors as those employed in the discussion of 

 F2. Assuming the zygotic formula of the Fi cross-bred cf to be 

 C^Bhf^Ii, and that of the black 9 to be C2h2Ffi2, the mating may be 

 represented : 



& CBfl • Cbfi • CBfi • Cbfl X 

 9 CbFi ' Cbfi = 



c^d^ { 



C2Bbf2li, white 

 0262^2^2, black 

 C2Bbf2i2, barred 

 C2b2f2li, white 



99 



CiBbFfli, white 

 C2b2Ffi2, black 

 C2BbFfi2, barred 

 C2b2FfIi, white 



Thus, according to the present hypothesis, there would appear in 

 F2, in every lot of 8 birds, the following types : 



