 As many studies, following up on the pioneering work of David Balme (1961, 1987b) have now established, the History of Animals (HA) is a work that from first to last displays and builds upon multi-differentiae division of animal differences (see Gotthelf 1988, 1997b; Lennox 2001b, chs. 1, 2; Pellegrin 1986). It is organized as a study of four kinds of animal differences first mentioned in HA’s first chapter as the principal objects of study (at 486b22–487a14)—differences in parts (the topic of Books I–IV), in modes of activity and ways of life (those related to generation in Books V-VI--and human generation in IX--others in Book VII) and in characters (Book VIII). These in turn are sub-divided; for example, discussion of the non-uniform parts (organs, as we say) of animals with blood (I 7-III 1) is followed by that of their uniform parts (tissues, III 2–22). A discussion of the parts of animals without blood then concludes the discussion of differences in parts (IV 1–8). Book IV concludes with a discussion of differences in sensory faculties, voice, and differences related to  sex.[9]