Alberto Varvaro (“Considerazioni sulla contaminatione…”, 191) rightly shifts the focus of the discussion to the causes of contamination, reviving the distinction between two types of perturbation in genealogical relationships:

1. contamination brought about by even partial reproduction of an editio variorum or an editio variorum in nuce (what Segre calls “contamination of readings” and Dutch stemmatologists “simultaneous contamination” or “contamination simultanée”).
2. contamination brought about by the replacing, from a given point in text onwards, of one model with another (definable as “contamination of exemplars“, or possibly even better as “contamination by juxtaposition of exemplars”, or, again following Dutch stemmatologists, “successive contamination” or “contamination successive“)