S4 MR. R. STAPLES-BROWNE ON [Feb. 18, 



had a darker down than those which became white. In Exp. 23 

 only two birds were raised ; eight other eggs were laid, but proved 

 unfertile. Exps. 21 and 23 produced blues with some white 

 feathers and whites in equal numbers ; on the other hand, Exp. 22 

 produced 1 blue and 5 whites. The result of the three experi- 

 ments being 5 blues to 9 whites. It may further be noted that 

 when Exp. 22, which is a repetition of Exp. 19, is reckoned with 

 Exp. 19, we get a result of 2 blues to 7 whites, the exact figures 

 found in Exp. 18. 



Discussion of Aberrant Results in Exps. 16 — 23. 



The expected result from these matings (DR x R) was an 

 equal number of blues (with white feathers) and whites. The 

 result obtained, however, was 13 blues to 28 whites. It is there- 

 fore necessary to analyse the results more closely. The only 

 matings which gave equality Avere 21 and 23, these gave 3 : 3 and 

 1 : 1 respectively. The ratio 2 : 4 was obtained in Exps. 16 and 

 17, and 1 : 2 in Exp. 20. Seeing that the total number of birds 

 produced in each family was small, the divergence of these ratios 

 from the expected equality would not suggest any very marked 

 irregularity. The totals, however, would point to the need for 

 repetition of the experiments with greater numbers. But when 

 we obtain the unlooked for result of 2 : 7 from Exp. 18 and from 

 the birds mated together in Exps. 19 and 22, we are forced to 

 conclude that some definite disturbing factor is present. The 

 following questions suggest themselves. Do the results obtained 

 from reciprocal matings differ ? Has the fact of the white parent 

 being a pure Fantail or an " extracted " any bearing on the 

 matter ? With regard to the reciprocal matings, only two matings 

 were made (Exps. 17 and 21) in which the c? was blue. These 

 gave ratios of 2 : 4 and 3 : 3 respectively. Dividing up our totals 

 according to the nature of the matings, we arrive at the following 

 figures: — When the d was white the offspring produced were 

 8 blues and 21 whites. When the S was blue the offspring pro- 

 duced were 5 blues and 7 whites. It will be noticed that, although 

 the whites are in excess in both cases, the divergence is much 

 more marked when the S was white. The possibility of this 

 having some influence on the proportions of the offspring cannot 

 at present be disregarded. The behaviour of the pure Fantail 

 and the extracted Wliite appears to be identical. Only two 

 extracteds were used : one of these in Exp. 21 gave a ratio of 3 : 3, 

 the other in the mating used in Exps. 19 and 22 gave 2 : 7, and 

 the same bird mated to another blue $ in Exp. 20 gave 1 : 2. 



In connection with the excess of white offspring when the d 

 was white, it is perhaps worth recalling that in certain remarkable 

 instances recessive forms appear in F. 1 when a recessive c? is 

 vised. The best ascertained example of this phenomenon occurs 

 in the Canary. Cinnamon (i. e. pink-eyed) 5 x gxeen {i. e. black- 

 eyed) (S gives F. 1 all black-eyed ; but black-eyed 5 x pink-eyed d 

 'may produce some pink-eyed birds, which are said to be always 



