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184   Life and Letters of Francis Galton

42, RUTLAND GATE. Nov. 5/75.

MY DEAR DARWIN, Three proofs reached me from the Contemporary Review of my `Theory of Heredity,' so I can spare one, and as I know you like to mark what you read, do not care to return it. I hope it will make my meaning more clear. The remarks printed as a note on p. 5, but which I ought to have put in the text, will meet what you wrote about the Hymenoptera.

I am most obliged for what you tell me about Brown-Sequard; I did not know of it, and will hunt up the passage to-day. (Thanks for the reference, received this morning.)

I should be truly grateful for criticisms which might enable me to modify or make clear before it is too late. Ever yours, FRANCIS GALTON.

What a nuisance this modern plan is, of sending proofs in sheet, and not in strip. One can't amend freely.

The paper which Galton sent Darwin is entitled `A Theory of Heredity.' This memoir was in type for the Contemporary Review in November 1875', and was read before the Anthropological Institute in the same month. It was revised and printed in the Journal of the Anthropological Institute (Vol. V, pp. 329-48), and it is to this issue that we shall refer. The paper follows generally the lines of the 'Blood-relation ship' of 1872, except that it still more definitely discards `.Pangenesis' and casts still further doubt on the heredity of acquired characters, and modification of offspring characters by the use or disuse of the same characters in the parent. The paper therefore marks a further stage in Galton's dissent from Darwin's theory and Darwin's views. Galton writes as follows

"The facts for which a complete theory of heredity must account may conveniently be divided into two groups; the one refers to those inborn or congenital peculiarities that were also congenital in one or more ancestors, the other to those that were not congenital in the ancestors, but were acquired for the first time by one or more of them during their lifetime, owing to some change in their conditions of life.

The first of these two groups is of predominant importance, in respect to the number of well-ascertained facts that it contains, many of which it is' possible to explain, in a broad and general way, by more than one theory based on the hypothesis of organic units. The second group includes much of which the evidence is questionable or difficult of verification, and which, as I shall endeavour to show, does not, for the most part, justify the conclusion commonly derived from it. In this memoir I divide the general theory of heredity into two parts, corresponding respectively to these two groups. The first stands by itself, the second is supplementary and subordinate to it." (pp. 329-30.)

After noting that Darwin, in the chapter on Pangenesis in the Animals and Plants..., had given the most elaborate epitome then extant of the many varieties of facts which a complete theory of heredity must account for, Galton states that his conclusions will differ essentially from Darwin's, and continues

"Pangenesis appears more especially framed to account for the cases which fall in the second of the above-mentioned groups2, which are of a less striking and assured character than those in the first rgroup, and it will be', seen that I accept the theory of Pangenesis with considerable modification, as a supplementary and subordinate part of a complete theory of heredity, but by no means for the primary and more important part." (p. 330.)

' It appeared in that Review in the following month. It was published also in the Revue Scientifcque, T. x, pp. 198-205, 1876.

2 Later on p. 347 Galton says that Pangenesis over-accounts for the facts of acquired modifications and reparations.