Page:Mendel's principles of heredity; a defence.pdf/130

mentally not very different from Galton's^[1]. It is an essential part of the Galton-Pearson Law of Ancestral Heredity that in calculating the probable structure of each descendant the structure of each several ancestor must be brought to account.

Professor Weldon now tells us that these two papers of Galton and of Professor Pearson have "given us an expression for the effects of blended inheritance which seems likely to prove generally applicable, though the constants of the equations which express the relation between divergence from the mean in one generation, and that in another, may require modification in special cases. Our knowledge of particulate or mosaic inheritance, and of alternative inheritance, is however still rudimentary, and there is so much contradiction between the results obtained by different observers, that the evidence available is difficult to appreciate."

But Galton stated (p. 401) in 1897 that his statistical law of heredity "appears to be universally applicable to bi-sexual descent." Pearson in re-formulating the principle in 1898 made no reservation in regard to "alternative" inheritance. On the contrary he writes (p. 393) that "if Mr Galton's law can be firmly established, it is a complete solution, at any rate to a first approximation, of the whole problem of heredity," and again (p. 412) that "it is highly probable that it [this law] is the simple descriptive state