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Show 86 MR, W. BATESON ON COLOUR-HEREDITY [May 26, Variegated black-and-white x chocolate-and-white gave on one occasion {Steer) 5 black-eyed whites and 1 chocolate-and-white. As mentioned above, blue may be recessive to black and breed true from its first appearance, and will doubtless prove to be a homozygous colour. We may now pass to a consideration of the crosses made with "Japanese" waltzing mice. The exact physiological nature of the waltzing habit seems to be still uncertain. Reference to the work especially of Cyon, Rawitz, and Zoth shows that, though malformation of the labyrinth is not infrequently associated with this condition, at least the degree of the structural malformation varies considerably. The origin of the variation is still more obscure. Mouse-fanciers have assured m e that something like it may appear in strains inbred from the normal type, though I cannot find an indubitable case. Such an occurrence may also be nothing but the appearance of a rare recessive form. Certainly it is not a necessary consequence of in-breeding, witness von Guaita's long series of inbred albinos. From analogy with other cases, we should be prepared to find that the existence of such a structural feature in one of the gametes had an effect on the colour of the heterozygote; but the evidence, as we shall see, is on the whole unfavourable to this view. As to crossing of waltzers and albinos, the earliest evidence is that of Haacke, whose records are qualitative only. Crossing waltzers, blue-grey with white marks, and albinos, he obtained mice generally self-grey (? agouti), more rarely self-black. Their offspring occasionally had a small white mark on the ventral surface. The next large body of evidence is that of von Guaita (19), who used black-and-white waltzers with dark eyes (von Guaita inlitt.) and an inbred strain of ordinary albinos. From this cross, Fx was always (from 4 pairs) a self-coloured house-mouse, and was also like that wild type in size (being larger than the waltzer and smaller than the albino) and in wild disposition. F2, raised from FT bred inter se, consisted of albinos and 4 coloured types-black, grey, black-and-white, grey-and-white. The totals were 30 coloured, 14 albinos. On the expectation of 3: 1 there should have been 33 and 11, so that the excess of albinos is distinct, though the numbers are small; but when all certain cases of D R x D R (taking albino as R ) are included, the numbers are 117 coloured and 43 albinos, coming very near indeed to the expectation 120 to 40. There can therefore be no doubt that the heterozygotes produced on an average equal numbers of albino gametes, and of gametes bearing the various colour-types. There are only two matings certainly in the form D R x R. These gave 23+1 coloured, 20+1 albinos, closely approaching the expected equality. In (20) Table I., from 1st and 5th pairs, we have families of 17 coloured and 13 coloured respectively, showing pretty clearly that |
