To understand the significance of the word “alternative” as introduced by Professor Weldon we must go back a little in the history of these studies. In the year 1897 Galton formally announced the Law of Ancestral Heredity referred to in the _Introduction_, having previously “stated it briefly and with hesitation” in _Natural Inheritance_, p. 134. In 1898 Professor Pearson published his modification and generalisation of Galton’s Law, introducing a correction of admitted theoretical importance, though it is not in question that the principle thus restated is fundamentally not very different from Galton’s[54]. _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._ [54] I greatly regret that I have not a precise understanding of the basis of the modification proposed by Pearson. His treatment is in algebraical form and beyond me. Nevertheless I have every confidence that the arguments are good and the conclusion sound. I trust it may not be impossible for him to provide the non-mathematical reader with a paraphrase of his memoir. The arithmetical differences between the original and the modified law are of course clear. 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 statement which brings into a single focus all the complex lines of hereditary influence. If Darwinian evolution be natural selection combined with _heredity_, then the single statement which embraces the whole field of heredity must prove almost as epoch-making as the law of gravitation to the astronomer[55].”