SummaryE. W. MacBride was one of the last supporters of Lamarckian evolution, and played a prominent role in the ‘case of the midwife toad’. Unlike most Lamarckians, however, he adopted a very conservative political stance, advocating the permanent inferiority of some races and the necessity of restricting the breeding of the unfit. This article shows how MacBride turned Lamarckism into a plausible means of supporting these positions, by arguing that progressive evolution is a slow process, and that degeneration of the (...) germ plasm takes place in unfavourable environments. In conclusion, it is suggested that MacBride's example shows that there are no intrinsic links between scientific theories and social views. These who insist on the social character of scientific knowledge must recognize that a theory may acquire different ideological links in different social environments. (shrink)