32 



CANARIES, HYBRIDS, AND BRITISH BIRDS 



III the first cross (P",) all the young are 

 dark-eyed and heterozygous, d being 

 dominant and p recessive. WTien these 

 young are interbred, the proportions ob- 

 tained are 3 dark-eyed to 1 pink-eyed, 

 3 to 1, 75 per cent, to 25 per cent. (Group 

 IV., 2, 3, 4). The 3 dark-eyed on being 

 tested are found to consist of 1 pure dark, 

 and 2 impure dark, so that the composition 



"X=> 



SILVER-GREY STARLING. 



Exhibttcd at the Crystal I'alace, I'JIO. by Mr. P. Walih. 

 (.See footnote p. 23.) 



of F^, is Id + 2 (d) 4- 1 ]>, or 25 per cent., 

 50 per cent., 25 per cent., the typical 

 Mendelian proportion. Of these the d 

 breed pure, and the p breed pure, but from 

 the 2 (d) the same proportions are again 

 obtained, viz., Id -I- 2(d) + Ip. The in- 

 heritance of eye colour, however, docs not 

 behave throughout in sinijiie Mendelian 

 fashion, being coni])li('alcd with the ques- 

 tion of se.x as already explained in con- 

 nection witli ciimanion inheritance. In 

 order to cx])lain on iNIcndclian lines the 

 results of the reciprocal mating to that 

 already given, viz., pink-eyed male x 

 dark-eyed female, it is necessary to refer 

 to the interesting parallel ease in the 

 Currant Moth {Abraxas grossulariata) given 



by Doncaster in Report IV. to the Evolu- 

 tion Committee of the Royal Society, 

 where the explanation of Bateson and 

 Punnett with regard to this mating is 

 given. They suppose that (1) femaleness 

 is dominant ; (2) that female individuals are 

 heterozygous in respect of sex, having the 

 constitution $ $ , and producing male- 

 bearing and female-bearing eggs in equal 

 numbers ; and that males are homozygous, 

 of constitution $ $ producing only male- 

 bearing spermatozoa ; (3) that there is a 

 gametic repulsion between femaleness and 

 the dark-eyed character. 



The following table gives their ex- 

 planation of this mating of homozygous 

 pink-eyed male heterozygous dark-eyed 

 female Canary : — 



As the same result is obtained with a 

 wild female, it is supposed that all wild 

 females of the Currant Moth are hetero- 

 zygous with regard to colour. 



This theory that all wild females are 

 heterozygous in colour is interesting from 

 the point of view of my theory of the evolu- 

 tion of all our Canary varieties from the 

 wild albinistic female, and, so far, in my 

 Canary matin^s of this description ((iroup 

 I.), my results are in accordance with the 

 theory. Nevertheless, it is doubtful if all 

 wild females are heterozygous in coloin-, 

 just as it is probably not the case that 

 the ordinary black-eyed hen Canaries are 

 necessaril\ hybrids (heterozygous) in the 

 ])ink-eye character, as su})i)osed by Dur- 

 ham and Marryatt (Report IV., Evolution 

 Committee of Royal Society, p. 60). For 

 I have had long experience of the much 

 inbred crested variety, pure dark-eyed both 

 on the male and female side ((Jmu]) IV.). 

 If the females had been heterozygous in 

 colour, some of the 283 young would 

 certainly have shown pink-eye, or cinnamon 



