OCR Text |
Show 1 9 0 5 .j HEREDITY IX PIGEONS. 5 5 7 T a b le III. E xp. No. ? . " . : ! i Also used (?• Also used N ature of Mating. " Shell." w a in Exp. ,ir go a in E xp. i 'i Present. Absent. 1901. a Nun - P ( 1 i&y Barb - A 7 liX I) 2 2 1902. 13 ... 8 a P - 54 a A - (? D RxDR) 2 1 1903. 7 ■■■ Nun - P ( l \&a Barb - A a Rxl ) 0 8 1904. 8 ... 1 7 A - 3 7 A - DR X DR 1 10 P = Presence of " shell," A = Absence of " shell." It will be noticed that as a result of the mating of Nun $ X Barb 3 in Exp. a, a mixed generation was obtained as regards " shell " in F. 1. The two birds in which the " shell " was absent were 3 , 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 smoothheaded 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 $ 8 (shell'* x Barb Fantail 3 gave 8 young. Barb Nun $ 18 (shell) X Barb Fantail 3 gave 5 young. Barb Nun 3 54 (no shell) X Barb Fantail $ gave G 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 oA h e 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 |