Freud, like many of his followers, had great difficulty in accepting the role of phylogenesis although without it we cannot understand such phenomena as intense sibling rivalry in an only child or the fact that wood can be a symbol for mother. Using dreams, a passage from the analysis of Little Hans, and other data, Fliess examines this question and concludes that one must at times 'supplement

individual with collective experience, historic with prehistoric material', even if it is hard to imagine how phylogenetic vestiges can exist.