Claim: Hamburger–Hamilton stages were modelled on an earlier system made for Axoloti, and provide advantages over the Carnegie system.
Evidence: Hamburger and Hamilton aimed to provide a detailed description of developmental events, modelled on an earlier system for Axolotl by Harrison. The Hamburger–Hamilton system provides advantages over the Carnegie system in that it allows the developing chick to be accurately characterized during all embryonic stages, and is used universally in chick embryology.