1905. | HEREDITY IN PIGEONS. DoT 
Taare ITT. 
| Bhp Nsw nese AIson | e 
peas | 9 ‘ S used 3 = S used | Netate sel. 
@, | = OD in 1 ge in | bate Sik 
| Og Exp. Se Exp. | Mating. Present. Absent. 
| | 
1901. | | 
a i Nun — P ee Barb — A Y | RxD 2 2 
| 
1902. | 
B 8  §o De Se eh = | @DEDR) 2 1 
none a 
1903 | 
Y soa) Wi = ee P ee Barb — A a | RxD 0) 8 
ahs é: | 
1904. 
| 
Cis el lapie y A — | 8 y A — | DRX DR 1 10 
P = Presence of “ shell.” 
A = Absence of “ shell.” 
It will be noticed that as a result of the mating of Nun 9° 
x Barb ¢ in Exp. «, a mixed generation was obtained as regards 
“shell” in F.1. The two birds in which the “ shell” was absent 
were ¢, the two in which it was present were 2. It was thus 
impossible to test the “shelled” birds by mating together, and 
little or no clue is obtained as to their gametic constitution by 
Exp. /3, as the numbers are so small. It may, however, be 
recorded that both the ‘ shelled” females and one of the smooth- 
headed males were mated subsequently to smooth-headed birds 
which were crosses in F. 1 between a Barb and a Fantail. From 
these matings : 
Barb Nun 2 8 (shell) x Barb Fantail ¢ gave 8 young. 
Barb Nun 92 18 (shell) x Barb Fantail ¢ gave 5 young. 
Barb Nun ¢ 54 (no shell) x Barb Fantail Q gave 6 young. 
Of these 19 birds so produced, none had “ shells.” 
In view of these results, which indicate that “shell” is a 
recessive character, the appearance of “ shells” in the two females 
mentioned above is paradoxical. It is likely that this 1s some 
failure of dominance and that the birds were gametically DR’s. 
A similar irregularity is recorded in the Report to the Evolution 
Committee of the Royal Society, i. p. 114, as regards extra toe 
in fowls, which, though generally dominant, is sometimes 
recessive. 
It was found inconvenient to follow up the experiment at the 
