To George Maw   31 August [1861]¹

Dear Sir

I write merely to say how grateful I shall feel for any facts on correlation or criticisms.— Will you sometime please explain a little more fully about the contracted corolla of the Pelargonium with the narrow leaves.—²

You put the difficult case of correlated changes in structure at Birth in a very striking manner. Such cases of correlation, however, interest me less than that of the Pelargonium: for according to my notions, (whether false or true) if the period of gestation became from any cause (& it does vary) shorter, if the milk did not flow, the inheritance of the new variation would be stopped by the death of the progeny; & thus a bond of apparent correlation might arise: but, I presume that no one will doubt that the case of the pelargonium is due to petals & leaves being homologous & similar at a very early period & being similarly affected by some unknown cause.—³

Cases of old or injured females assuming male attributes is perhaps even more curious than the effects of castration on males.—

I shall be truly glad to hear any facts, when you have leisure & inclination to write to me & I beg leave to remain | Dear Sir | Yours sincerely | Charles Darwin