Andrea Pitzer: In Jeffrey Meyers' Edmund Wilson: A Biography, Meyers notes that Nabokov used the term "a salad of racial genes" (p. 286) to describe Wilson's fourth and last wife, Elena Mumm Thornton, who was German and Russian. The phrase, of course, is the same that HH uses to describe his father in Lolita. The quote is not sourced...( Nab-L 14 Mar 2010)

JM: I just got another link to an old TNR review --R.W. Flint's 1957 review of Lolita-- (http://www.powells.com/review/2003_07_17.html%20) from Jim Twiggs, a propos "Lolita" and "Gogol." (comic/cosmic). I found a description in it that reminded me of Pitzer's query: "Suffice it here to say that Lolita's chief actor, Humbert Humbert, a Swiss "salad of racial genes," is afflicted with about equal degrees of wit, ennui, taste and a hideously overt form of nympholepsy; the disease of Ruskin and Lewis Carroll given free and tender rein in a wilderness of American motels, suburbs and progressive institutions. Lolita is a burlesque of Freudianism that Freud would have had to enjoy." 

The familiar reference from Lolita, I, ch.2 (AL,p.9): "I was born in 1910, in Paris. My father was a gentle, easy-going person, a salad of racial genes: a Swiss citizen, of mixed French and Austrian descent, with a dash of the Danube in his veins. I am going to pass around in a minute some lovely, glossy-blue picture-postcards. He owned a luxurious hotel on the Riviera,"  after I read it again (after having searchedfor the "salad" in the EW/VN correspondence in vain), led me to conclude that most probably Jeffrey Meyers's unsourced reference to Elena Mimm Thornton was some kind of mistake on  his part. I don't think Nabokov would have enjoyed mingling Elena and HH's father...