This paper aims at examining the way in which Aristotle deals with the problem of genetic malformations, developed, in particular, in The Generation of Animals (Book IV), within the theory of the genetic inheritance. According to this doctrine a malformation represents a deviation from the teleological development of the reproductive process, whose first step is represented by a female birth. Even though necessary for the continuation of the species, this event is described within the same theoretical frame of the genetic anomalies by Aristotle, who is committed to provide some prescriptions about mating and reproduction, in order to prevent this departure. In general, the issue of malformations highlights the presence of the material and mechanical aspect of the nature which, at times, can support or obstruct its teleological design, but which constitutes one of the fundamental assumptions of the physis.
