CD agrees cultivated plants may begin to vary after some time and then may vary suddenly, but cautions JDH on lack of evidence. His explanation is that small variations are ignored until they accumulate.
Down Bromley Kent
My dear Hooker
I have the old M.S, otherwise the loss would have killed me! The worst is now that it will cause delay in getting to press, & far worst of all I lose all advantage of you having looked over my chapter, except the third part returned.— I am very sorry Mrs Hooker took the trouble of copying the two pages.—
Do not, pray, think of giving up coming here; I
I much fear after all we shall not be able to send for you: but let me know train by which you will come to Bromley (Mason Hill) & then I will send if I can, if not you must take fly, & always plenty there.
I would advise you to be cautious about stating so broadly (I thought that you perhaps knew of distinct cases unknown to me) about species not varying for many generations & then suddenly varying. To a certain extent I quite believe it; ie that a plant will not vary until after some few generations (perhaps dozen or so) & then will begin to vary possibly suddenly, more likely gradually. But even my belief in this is grounded on very few facts.— I believe another & very distinct explanation may be given of a sort of current belief in the doctrine, viz that variations are often not attended to, & till they are attended to & accumulated, they make no show.—
Ever yours | C. Darwin
I have worked this notion up in (as it seems to me) an important manner in my Ch. on Domestication of Animals & Plants.
- f1 2453.f1Hooker had accidently put the fair copy of CD's chapters on geographical distribution in the drawer in which Frances Harriet Hooker kept paper for the children to draw on. In a letter to Thomas Henry Huxley, Hooker related how the children ‘of course had a drawing fit ever since’ so that nearly a quarter of the manuscript had vanished before Hooker came to read it (L. Huxley ed. 1918, 1: 495–6). Hooker continued:
I feel brutified, if not brutalised, for poor D. is so bad that he could hardly get steam up to finish what he did. How I wish he could stamp and fume at me—instead of taking it so good-humouredly as he will.
- f2 2453.f2The Darwins were expecting Emma's brother Francis Wedgwood and his family from Barleston, Staffordshire. In addition to Hooker, the two Thorley sisters came, presumably to help with the children.
- f3 2453.f3See Origin, pp. 41–2, where CD cited the example of the strawberry:
I have seen it gravely remarked, that it was most fortunate that the strawberry began to vary just when gardeners began to attend closely to this plant. No doubt the strawberry had always varied since it was cultivated, but the slight varieties had been neglected. As soon, however, as gardeners picked out individual plants with slightly larger, earlier, or better fruit, and raised seedlings from them, and again picked out the best seedlings and bred from them, then, there appeared (aided by some crossing with distinct species) those many admirable varieties of the strawberry which have been raised during the last thirty or forty years.Hooker discussed the point in Hooker 1859, p. viii.