Pattern formation in early developmental stages of amphibian embryos

ABSTRACT The causal morphological analysis of the determination and differentiation processes in early developmental stages has been successfully carried out, especially in insects, sea urchins, amphibians and mammals. In all these investigations the final outcome of isolation and transplantation experiments has been evaluated by histological analysis of the differentiated tissues. In such experiments the term determination, which has been used in several ways, can be defined as follows: A certain region of a cleaving egg or an embryo is said to be determined if after isolation it forms the same tissues as in the intact embryo.