"A Series of Normal Stages in the Development of the Chick Embryo" (1951), by Viktor Hamburger and Howard L. Hamilton

The developmental stages [4] of the chick [5] embryo were examined by Viktor Hamburger [6] and Howard L. Hamilton [7] in ?A Series of Normal Stages in the Development of the Chick Embryo,? published in the Journal of Morphology [8] in 1951. These stages were published to standardize the development of the chick [5] based on varying laboratory conditions and genetic differences. The stages Hamburger and Hamilton assigned were determined by the visible features of the chick [5] embryo. The first stage begins just prior to the primitive streak [9] , with the formation of the embryonic shield, and the final stage, forty-six, ends at the hatching of the chick [5].