Studies on Pregastrular Development, Early Embryonic Development, and Hatchability of Prematurely Laid Eggs of the Hen

A NUMBER of workers, including Dareste (1877), Mitrophanov (1900), Tannreuther (1919), Newman (1940), and others have reported and described various types of monsters and duplicities in the chick embryo. Nalbandov (1942) reported one case of viable twin chicks, presumably of monozygotic origin. Stockard (1921), stated, “in spite of many experimental studies on the developing hen’s eggs by Dareste, Fere, the writer, and others, no double monster, or twin conditions have been produced.” Twieselmann (1935) and others have produced doubling in the chick embryo by injury to the blastoderm, and Waddington and Schmidt (1933) have induced secondary embryos by transplantation of organiser material. Stockard’s theory, that an arrest of development in pregastrula stage embryos caused twinning and double monsters, was tested by Riddle (1923) on pigeons and doves. He obtained eggs from these species at various stages of development before gastrulation and, after cooling them, subsequently incubated them. These eggs were . . .