 HA V-VI discuss all aspects of animal generation, moving from consideration of differences in modes and timing of copulation and reproduction to the actual process of generation (or ‘development’, as we more often say). As in his discussion of parts, he moves through the various blooded kinds and then discusses generation in bloodless kinds and from identifying the universals common to all members of a group to identifying the peculiarities of more specific kinds. At HA VI 3, having previously described the common and peculiar characteristics of copulation in birds, he turns to recording his observations of the development of the chick at the critical fourth day after the egg has been laid.