and in the latter the ratio
1 DR : 1 RR.
The DD group and the RR group thus produced giving on self-fertilisation pure D offspring and pure R offspring respectively, while the DR groups gave again
1 DD : 2 DR : 1 RR.
How does Professor Weldon propose to deal with these results, and by what reasoning can he suggest that considerations of ancestry are to be applied to them? If I may venture to suggest what was in Mendel’s mind when he applied this further test to his principles it was perhaps some such considerations as the following. Knowing that the cross-breds on self-fertilisation give
1 DD : 2 DR : 1 RR
three explanations are possible:
(a) These cross-breds may produce pure D germs of both sexes and pure R germs of both sexes on an average in equal numbers.
(b) Either the female, or the male, gametes may be alone differentiated according to the allelomorphs, into pure D’s, pure R’s, and crosses DR or RD, the gametes of the other sex being homogeneous and neutral in regard to those allelomorphs.
(c) There may be some neutralisation or cancelling between characters in fertilisation occurring in such a way that the well-known ratios resulted. The absence of and inability to transmit the D character in the RR’s, for instance, might have been due not to the original purity of the germs constituting them, but to some condition incidental to or connected with fertilisation.