1905.J 



HEREDITY IN PIGEONS. 



Table III. 



557 



P = Presence of " shell." 

 A = Absence of " shell." 



It will be noticed that as a result of the mating of Nun 2 

 X Barb S in Exp. a, a mixed generation was obtained as regards 

 " shell " in F. 1. The two birds in which the " shell " was absent 

 were d" , the two in which it was present were 5 . 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 ISTun $ 8 (shell) x Barb Fantail S gave 8 young. 

 Barb Nun 5 18 (shell) x Barb Fantail S gave 5 young. 

 Barb Nun S 54 (no shell) x Barb Fantail 2 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 is 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, ii. 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 



