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Chick Embryo staging In order to repeat a published experiment, or have someone else repeat yours, it is important to use the same materials. For developmental studies, that means knowing the precise point in development that the embryos have reached. The time of incubation gives only an approximation of the developmental age. For this reason, staging series based on morphologic criteria have been prepared. Chick embryos have been incubated by the hens for different amounts of time before collection and they develop at different rates depending on the temperature in the incubator. Chick embryos are usually staged according to a series prepared by Victor Hamburger and Harold Hamilton [J. Morphol. 88:49-92 (1951), reprinted Develop. Dynam. 195:231-272 (1992)]. For a poster of this classic, visit the Developmental Dynamics website. Eyal-Giladi and Kochav [Dev. Biol. 49:321 (1976)] have prepared an expanded series that allows early embryos to be staged with more precision. Click here for labeled photos of living chick embryos A set of fixed and stained embryos staged according to Hamburger and Hamilton (1951).