R. Staples-Browne 147 



this family were heterozygous in this character, and two blue rumped birds 

 were to be expected in a family of seven. With such small numbers, 

 however, the appearance of only one is not surprising. 



Eitp. 54. Blue chequer, few w.f. $ 63 x Blue chequer, several w.f. 



These two F^ birds, raised in Exp. 52, were mated together and 

 produced 11 young. Of these one was blue with no white feathers, 

 another blue with two white feathers on the rump and a very few on the 

 vent and thighs. The remarks on a similar bird produced in the last 

 experiment are equally applicable to this specimen. The other coloured 

 birds produced from this mating all had a considerable amount of white 

 in their plumage. Of these three were non-chequered, whilst four were 

 chequered. White feathers were present on the head, neck, rump, 

 vent, thighs, abdomen, often on the breast ; also there were white flight 

 feathers, tertiaries, bastard wings, and sometimes one or more tail 

 feathers. In addition to the coloured birds already enumerated, two 

 whites were produced. 



Exp. 55. Blue, much white $ 51 x Blue, much white (^ 3. 



These two birds, raised in Exp. 54, had white feathers on the head, 

 neck, rump, vent, thighs, flights and tertiaries. The ^ had white on 

 abdomen and bastard wings in addition. The young produced were : 



One blue with very few white feathers, viz. six white feathers on the 

 rump, and one white flight feather tinged with blue, six of the blue 

 with much white type, and four whites. 



In this case we are dealing only with one pair of allelomorphs, the 

 presence and absence of blue. The expectation is 3 blues : 1 white. 

 Of the blues one would have no white whereas two would show white 

 feathers. The fact that the blue with very few white feathers occurs 

 where blue with no white is expected, and the contrast between this 

 bird and the other coloured offspring is so marked, is very suggestive 

 that this type is the homozygote which has not segregated quite cleanly. 

 The expected ratio is 2*75 : 5*5 : 2'75, the observed figures 1 : 6 : 4. The 

 discrepancy is not very great for so small a total It is also seen here 

 that the coloured type with much white is dominant to that with 

 only a few white feathers. It is possible that this is connected with the 

 dominance of the white rump. 



