R. Staples-Browne 



145 



explanation of this being that the Fi birds raised in Exp. .52 were 

 heterozygons in the factor for chequering, and produced in Exp. 54 

 birds homozygous for non-chequering, of which the white $ 4 used in 

 this mating was one. 



Exp. 51. Blue, several w.f $ 7 x Blue, several w.f ^ 6. 



These were the two F-^ birds raised in Exp. 50. They produced 

 seven young, of which six were raised to maturity. These con.sisted of 

 four birds similar to the parents^ and two almost identical with C. livia. 

 The white feathers on the rump were not quite so extensive as in the 

 Rock Dove, but there were no white feathers elsewhere, showing that 

 the pattern-factor had segregated out fairly cleanly. It was remarkable 

 that from the crosses of the Lincolnshire Rock Doves with Whites no 

 typical C. livias were extracted ; this may possibly be accounted for by 

 the fact that the Lincolnshire bird used was heterozygous in respect to 

 rump-character, as has already been shown in Exps. 47 and 48. In 

 addition to the six birds already described for the present mating, one 

 young bird was produced which died on hatching. It had white down 

 and white beak and claws. Since the blues have yellow down and 

 some black on the beaks and claws, I have no hesitation in recording 

 this as white. The F„ generation, here produced, is therefore, 2 Typical 

 G. livia, 4 Blues with several white feathers, and 1 White, and is in 

 very close agreement with the Mendelian ratio 1:2:1 which is the 

 expectation for this mating. 



Exp. 52. White Fantail ? 40 x Typical C. livia ^ 44. 



This blue rock dove </, raised in Exp. 47, is the same bird that was 

 used in Exp. 48, where it was shown to be heterozygous as regards the 

 colour of the rump. A family of eight birds was raised from this mating. 

 All were of the chequered type, with varying amounts of white feathers. 



