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Show 80 MR. W. BATESON ON COLOUR-HEREDITY [May 26, On breeding specimens of each type inter se he found the following behaviour:- Type 1 might give Types 9 n a n 11 n n <> n n 11 11 4: ,, ,, ,5 K 5) " ?! 11 " 11 " ,, ,, „ J) ' 11 11 H In other words, each type is dominant to albino and the wild type is dominant to all. The grey forms are dominant to the black. The black-and-white of type 5 is recessive to type 6, (black with white markings), but the self-coloured black does not contain type 5. These are some of the deductions from the table. The peculiarities of types 3 and 5 are especially noteworthy and call for fresh experimental study. It appears that types 3 and 5 could be ultimately bred true. As to 6 and 7 the evidence is not very clear; but as I understand the account, neither was completely freed from throwing the other. The breeding in these types was the least successful and extensive. Possibly they are illustrations of the Mittel-rassen of de Vries. It is especially noteworthy that the grey-and-white type 3 and the black-and-white type 5 do not give rise to self-grey gametes or to self-black gametes, a fact found again in mice. W e see therefore that there are gametes for black-and-white and for grey-and-white, each of which may behave as a single character and dominate over albino. Similarly when pure black-and-white was crossed with the wild species, all the coloured types might appear in F2 but no albinos (10. pp. 555-6). Therefore, in this very important case, when black-and-white of type 5 appeared in the posterity of such a cross, they were all homozygotes and produced only their own type (p. 555). This fact may furnish a useful basis for a new experiment. In strict accordance with our expectation, Crampe found that black-and-whites which gave albinos when bred inter se, gave albinos if crossed with albinos; but when they did not produce them themselves, they did not when bred with albinos. The similar variety, grey-and-white (type 3), is always homozygous except when it appears as a dominant containing types 4 or 5. But if I rightly understand Crampe's use of the word " constant," type 5 is not produced by crossing type 3 with the wild form, unless it was already brought in as recessive to type 3. On the other hand, type 3 can be produced (in F2) by crossing type 5 with the wild form. It is most desirable that the properties of these two types (3 and 5) should be fully explored. They give a chance of investigating the resolving powers of a recessive that is not albino, and free from several complications attending the use of the latter. W h e n wTe try to picture what is taking place in the resolution 1 2 4 6 7 1 2 3 4 5 6 7 3 4 5 4 4 5 4 5 6 7 4 6 7 |
