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Show 92 MR. W. BATESON ON COLOUR-HEREDITY [May 26, while the dark-eyed blacks should give only blacks, perhaps blues, and albinos. The dark-eyed greys will probably give both blacks and yellows, though in view of von Guaita's evidence that grey may exist as a new homozygote, this is perhaps doubtful. As far as the published evidence goes, the most probable constitution of the several forms in F2 is as follows:- Albinos albino x albino. Pink-eyed yellows yellow x yellow. Dark-eyed yellow x albinos. Pink-eyed fawn-yellows ... fawn-yellow x fawn-yellow. Dark-eyed blacks black x albino (?) Dark-eyed greys fawn x albinos (and perhaps some other combinations). Pink-eyed lilacs lilac x lilac. The absence of blacks with pink eyes is noticeable, and raises the question whether there is not a permanent synthesis in these blacks. Finally, we have two important problems, the nature of the dark-eyed fawn-yellows and of the dai-k-eyed " lilacs." As they are dark-eyed they presumably both contain albino. But as regards the first, it is difficult to see what the other gamete can be in that case. For from Fx we learn that fawn X albino give grey, not fawn-yellow. On the other hand, as there are black and yellow gametes, we ought to find their heterozgyote, which will presumably be fawn. But if this combination follows the rules of the others, the heterozygote should be pink-eyed, not dark-eyed. The number of dark-eyed fawn-yellows, three, is too few to make it likely that these are the black x yellows, which we expect to appear as a fairly frequent combination ; and the general indications are quite unfavourable to the view that any considerable number of heterozygotes can be dark-eyed without the presence of the albino, though it is not impossible that such real synthesis may take place. Next the " lilacs" raise certain questions. W e must suppose that the dark-eyed " lilacs " contain albino ; but in the offspring of F, x albino there are no " lilacs." As F: is giving off gametes capable of forming " lilacs," we see that the lilac x pure albino gives some other colour. Next, which of the groups can be supposed to represent the lilac-bearing gametes in then other combinations ? This also is a question we cannot answer. A similar difficulty is created by the scarcity of yellows in the offspring of Fx x albino. There were only 3 in 88. W e might have expected the numbers of yellows and blacks to be equal, but there were 15 blacks. Moreover, all the yellows were in one family. So far this is quite inexplicable. It probably indicates that some of the albinos possessed powers of resolution different from those of others, or conversely that some of the original " fawns" were more easily resoluble than others. \cf. Cuenot's new results (27), where blacks were resolved out, but apparently no yellows.] |
