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Show 88 MR. W. BATESON ON COLOUR-HEREDITY [May 26, calling for elucidation is the distinction between the black-and-white of the original waltzers and the black-and-white of subsequent generations. Fj from albino and the waltzers was the atavistic grey, but there is no indication that the subsequent heterozygotes between blw. and albino were grey; or more strictly there is a great deal of evidence that they were usually blw. The suggestion also that the atavistic colour was due to the union of the waltzing and non-waltzing character seems to be plainly excluded, because even normal albinos in later generations proved to be heterozygotes of waltzing and non-waltzing gametes. At present, therefore, we cannot declare what was the difference between the original pure gametes which caused the reversion when they were united. Lastly, there is a difficulty, perhaps the most serious of all, in the result of the union of albino x self-grey (19. p. 328, 2nd pair, both parents being in F2) which gave 13 grey, 3 grey-and-white. I see at present no suggestion as to the gametic production of the grey parent in this case which can be made with any probability, consistently with the other facts. Possibly the diversity of gametes lay with the albino. I now pass to an examination of the evidence of Darbishire, who crossed ordinary albino mice with waltzers. The waltzers used were " pale fawn "-and-white with pink eyes, thus outwardly corresponding somewhat with one of the breeds of rabbits called " Himalayan." The nature of the pigmentation described as " fawn" is not specified; but from the results, and especially from the distinction drawn by the author between "fawn," " fawn-yellow," and " yellow," there can be little doubt that the fawn was composed of both yellow pigment and a dark pigment, probably black. Twenty-nine pairs were used in the production of P r The offspring of 23 of these pairs, 120 individuals, had grey colour. All except one had more or less white or whitish, differing in extent. Some had more white than the waltzers, while in others the whitish colour only appeared on the belly! The pure albinos gave on the whole more fully coloured, the extracted albinos less fully coloured heterozygotes. The tint of the grey is further classified into "pale wild colour" and " dark wild colour," both being stated to be such as occur in musculus. Full details as to distribution are given {q. v.). Of the remaining six pairs, four gave one or more mice with the colour-patches black (with grey brethren in three families) as follows:- pa{r Patches. Grey. Black. XXYII i LXXYII 1 3 LXXYIII 4 3 L X X X V 6 2 11 9 |