Embryology of the emperor penguin (Aptenodytes forsteri)

E. A. Wilson1 wrote in 1907, “The possibility that we have in the Emperor penguin the nearest approach to a primitive form not only of a penguin but of a bird, makes the future working out of its embryology a matter of the greatest possible importance”. With this aim in mind he set out on June 27, 1911, with Bowers and Cherry-Garrard on a terrible journey2 in the antarctic winter, during which three embryos were obtained from the Cape Crozier rookery on July 20. These specimens were described by Parsons3, who considered that the smallest one corresponded to a chick embryo of ten days incubation, whereas the two larger specimens corresponded to chick embryos of thirteen days incubation.