The following methods comprise a brief description of chick egg incubation and embryo harvesting. For further details concerning optimizing embryo viability during incubation, the reader is referred to the excellent work of New (1 ). Embryos are staged according to the staging series devised by Hamburger and Hamilton (2 ), which has recently been reproduced (3 ). The reader is also referred to Chapter 15 . A further, detailed staging series for very young embryos has also been devised (4 ).
