What happened was that Aveling's mistress was Marx's daughter, and when both Darwin and Marx were dead, Marx's papers became muddled up with Aveling's papers, and a letter from Darwin saying, "My dear sir, thank you very much but I don't want you to dedicate your book to me," was mistakenly supposed to be addressed to Marx, and that gave rise to this whole myth, which you've probably heard.
Hvad der skete, var, at Avelings elskerinde var Marx' datter, og da både Darwin og Marx var døde, blev Marx' papirer rodet sammen med Avelings, og et brev fra Darwin, hvori der stod: "Min kære Herre, mange tak, men jeg ønsker ikke, at De dedikerer Deres bog til mig" blev fejlagtigt antaget, som rettet til Marx, og det gav anledning til hele denne myte, som I sikkert kender.