To A. R. Wallace [6 February 1866]1
Down Bromley SE
My dear Wallace
After I had despatched my last note, the simple explanation which you give had occurred to me, & seems satisfactory.2
I do not think you understand what I mean by the non-blending of certain varieties.3 It does not refer to fertility; an instance will explain; I crossed the Painted Lady & Purple sweet-peas, which are very differently coloured vars, & got, even out of the same pod, both varieties perfect but none intermediate.4 Something of this kind I shd. think must occur at first with your butterflies & the 3 forms of Lythrum;5 tho’ these cases are in appearance so wonderful, I do not know that they are really more so than every female in the world producing distinct male & female offspring.
I am heartily glad that you mean to go on preparing your journal.6
Believe me yours | very sincerely | Ch. Darwin
ARW’s simple explanation of dimorphic forms is satisfactory.
On "non-blending" of certain varieties, CD thinks ARW has not understood him. He does not refer to fertility. He crossed two differently coloured varieties of peas and "got both varieties perfect, but none intermediate". Something like this must occur in ARW’s butterflies.
Please cite as
Darwin Correspondence Project, “Letter no. 4989,” accessed on 29 August 2016, http://www.darwinproject.ac.uk/DCP-LETT-4989