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484   Life and Letters of Francis Galton

I want to ask you about a possible experiment with the Illustraria-of which I am allowed to rear another set. You remember that though the ratio between the races is the same whether the creatures are reared by Miss Pridham, by Mr Merrifield, or by myself, yet the absolute size of each race varies. Call the mean size of Mr Merrifield's A race= A.. I receive eggs whose inherited tendency should be to vary about Am as a Median. The resultant moths vary about something else = A,,, as a Median. It appears that the offspring of my moths, reared at Brighton, vary again about A.,. Therefore the increase of size causing the median value of the race to rise from A. to A,;, was not inherited. This seems a very typical instance of an "acquired" character. Would it be worth while to devote a few spare pairs of one set to the foundation of a race which should live for several generations here in Plymouth, 'and should then be returned to Brighton-in order to see through how many generations the external conditions can act without producing an inherited change?

I shall be here till the end of this year, = 2 generations, and I can easily find someone at the Laboratory who will deal with the following generations. .

Yours very truly, W. F. R. WELDON.

I believe I have not yet thanked you for your kind congratulations on the action of the Royal Society.

30A, WIMPOLE STREET, W. October 29, 1891.

DEAR MR GALTON, I hope to send you, in a little while, detailed tables of the correlations of which I spoke to you this morning in the Senate House. The organs are the four which I had previously used in the Shrimp : and the rough figures for the relation a to b or 6 to a are at present

Plymouth race    (1000)    0.84

Roscoff (Finistere)    (500)    0.88

Southport   (400)    0.83

Sheerness    (380)    0.85

The values obtained for each deviation clustered about the line r=0.85 so well that I thought it worth while to determine the second place of decimals by taking the arithmetic mean of all observed ratios in each case. Between character b and "telson length" the ratio is

Plymouth    0.25

Roscoff    0-29

Southport    0.30

All the other values are, in the Plymouth race, so small that I have not thought it worth while to determine them in the other races at present, because of the small number of individuals in each sample. But I have just obtained, and nearly measured, 400 additional Shrimps from Southport: so that I hope soon to have a set of 800 measures of this race, which will give a fair basis of comparison with the 1000 from Plymouth. When these preliminary determinations are finished, I hope to determine a reasonably numerous set of constants for homologous organs in one or two species. An enthusiastic student, to whom I have preached you, has already undertaken to measure 20 organs in each of 1000 Prawns.

Yours very truly, W. F. R. WELDON.

Selection of Galton's Letters to Mr Howard- Collins dealing with Finger-Print Data*. .

HOTEL CHERBOURG, VICHY,'ALLIER, FRANCE. August 19, 1891.

DEAR MR COLLINS, You must have thought. me very forgetful of your most kind offer to help in some of the matters over which I bother myself, and in which I am making far too slow progress. But in truth I have been very far from forgetful, and have delayed only through difficulty in seeing the direction in which I could reasonably ask your help. And the difficulty is not yet overcome, because as a rule my work is in no respects straightforward, but I have to plan as I proceed, and am consequently much bewildered between theory and detail. There is

* These letters, with a considerable amount of Galton's unpublished material on finger-prints, were purchased by his biographer from a Birmingham bookseller.