 Another important set of studies is of the polymorphic Scarlet Tiger Moth, Panaxia dominula (see Provine 1986 for extended discussion, to which the following is indebted). Fisher and Ford deliberately chose P. dominula because of its small population sizes, figuring that if they could make the case for selection against drift in its worst case, they could make a decisive case against Wright, who they saw as advocating a form of nonadaptive evolution. But rather than trying to make a case for selection, as Cain and Sheppard did, Fisher and Ford (1947) tried to make a case against drift by arguing that the fluctuations of gene frequencies across generations were too large to be accounted for by drift and that the size of the fluctuations did not differ between the small and the large populations, as you would expect if they were undergoing drift. Therefore, they concluded, the populations were undergoing selection. Wright’s (1948) reply challenged both the logic of this conclusion (disproving drift does not prove selection) as well as their characterization of his views, but more significantly, he pointed out that Fisher and Ford had not included data on population sizes for the years in which the gene frequency fluctuations were statistically significant, so, in fact, it was possible that the populations had been undergone constrictions in those years, in which case drift would have been able to produce the observed fluctuations. He also pointed out that fluctuations in selection or migration (which he very problematically suggested could be part of an expanded understanding of drift) could have produced the same outcomes.