Amphibian embryos provide excellent material for understanding the establishment of the vertebrate body plan during early development. Fertilized eggs are readily obtained by hormone-induced spawning, and their developmental rate can be adjusted by ambient temperature regulation. Eggs and early embryos are large enough in size for surgical manipulations, especially when compared with eggs of other vertebrates. Also, embryos and isolated embryonic tissues can be easily cultured for a minimum of several weeks in a simple salt solution containing antibiotics. These advantageous features of amphibian eggs and embryos have led to the discovery of the primary embryonic organizer, various inducing factors, and a variety of cellular events involved in inductive interactions.
