V.—The Early Stages in the Development of the Ferret: The Formation of the Mesoblast and Notochord

Abstract

In a former memoir (1934) the author described the early development of the ferret from fertilisation to the formation of the prochordal plate. The following is a continuation of that work and describes the development of the mesoblast and notochord from their incipient phases to a stage with seven somites when the definitive notochord begins to separate from the notochordal plate. As far as can be ascertained these phases have not been previously described in the case of the ferret, although the literature on gastrulation and the formation of the notochord and mesoblast is voluminous. A résumé of the descriptions and theories of gastrulation has already been fully summarised by Rabl (1915), and later by Van Oordt (1921). Opinions concerning notochord and mesoblast formation will be referred to in the following pages, and as there is great confusion of nomenclature in it I have appended a Glossary of the terms which I have used and the meanings that I attach to them (p. 188).