Historia Animalium Book X

"Among the extant Aristotelian writings are ten books that have survived under the title Historia Animalium or Researches into Animals (henceforth HA). Some of the ancient catalogues of Aristotle's works list ten books in the HA, some only nine. Among the latter, but not the former, there is also mention of a treatise (On Failure to Reproduce). It seems almost certain that this title refers to Book X, which deals exclusively with human sterility and fertility, and therefore that it was originally meant to stand as an independent work, a fact which explains its evident failure to fit in with the overall schema of the HA. Theodore Gaza's 476 translation was made from several mss. which included Book X, including those of the [beta] family and possibly Guil., but he deliberately omitted it.1 The consensus of scholarly opinion since then has been that the text we possess as HA X was originally composed as a separate freestanding treatise, On Failure to Reproduce"--