 Having developed this general explanation during his discussion of his central case, viviparous development, in GA II, Aristotle moves on to egg-laying animals in book III. GA III 1 carries over to them whatever is common to the two cases, with discussion of the development of birds in their eggs beginning in GA III 2. A recurring aspect of his argument, here as in PA, is to refer us for descriptive details to the histories (presumably the basis of our HA) and to a collection of representations of dissections (tragically not preserved, but cited repeatedly in Aristotle’s biological writings and in ancient catalogues of his writings).