The difficulty or impossibility of drawing up a satisfactory classificatory system from the Aristotelian writings has not, however, deterred numerous naturalists and scholars from making the attempt, and the subject has in itself a considerable history and literature[51] extending from the days of Edward Wotton (1492-1555) downward.[52] The more recent efforts at drawing up an Aristotelian classificatory system have been based on the methods of reproduction to which he certainly attached very great importance.[53] Provided that it be remembered that Aristotle does not himself detail any such system there can be no harm in constructing one from his works. At worst it will serve as a _memoria technica_ for the extent and character of his knowledge of natural history, and at best it may represent a scheme to which he was tending. [50] _De partibus animalium_, i. 4; 644ᵅ 16. [51] The classificatory system of Aristotle and its history are discussed in great detail by J. B. Meyer, _Aristoteles’ Thierkunde: ein Beitrag zur Geschichte der Zoologie, Physiologie und alten Philosophie_, Berlin, 1855. [52] The work by which Wotton is known is his _De differentiis animalium_, Paris, 1552. [53] There is a valuable chapter on the subject of the Aristotelian classificatory system as based on the method of reproduction in W. Ogle, _Aristotle on the Parts of Animals_, London, 1882. _ENAIMA_ (_Sanguineous and either viviparous or oviparous_) = _vertebrates_. { 1. ἅνθρωπος. Man. { 2. κήτη. Cetaceans. { 3. ζῷα τετράποδα ζωοτόκα ὲν αὑτοῖς. { Viviparous quadrupeds. { (a) μὴ ἀμφώδοντα. Non-amphodonts Viviparous in the { = Ruminants with incisor in internal sense. { lower jaw only and with cloven { hoofs. { (b) μώνυχα. Solid-hoofed animals. { i. λόφουρα. Equidae. { ii. μώνυχα ἔτερα. Other solid-hoofed animals.