The Localization of the Presumptive Cerebral Regions

O N E of the most important means of studying the phenomena of induction and determination during the development of the central nervous system consists in microsurgical operations of different kinds on the neural plate of Urodela. Hence it is important to have the neural plate mapped with regard to the prospective significance of its different parts, the 'materielle Anlagen' of Mangold (1937). A detailed mapping of the caudal part of the neural plate has been carried out by Nakamura (1942). Earlier attempts to map the entire presumptive brain are due to His (1893) who, however, used a very crude method, and to Waechter (1953) who examined the ability to differentiate of material from different parts of the neural plate. Investigations of this kind have also been performed by other authors (Mangold, 1933, 1937, 1955; Mangold & v. Woellwarth, 1950; Raven, 1935; Alderman, 1935; v. Aufsess, 1941; ter Horst, 1947) who were, however, not so confident of the interpretation of their results as to synthesize them in a map of prospective areas. The results of microsurgical operations on the neural plate also provide information about the localization of presumptive regions (e.g. v. Aufsess, 1941; Horstadius & Sellman, 1946; Raunich, 1951; Sladecek, 1952 and 1955). More reliable is the vital staining method of Vogt (1925). This method has been used by several students who, however, all aimed at the examination of a limited area, either the eye field (Petersen, 1923; Woerdeman, 1929; Manchot, 1929) or the neural crest (Baker & Graves, 1939; Fautrez, 1942; Horstadius & Sellman, 1946). There has been special interest in the position of the presumptive eye areas, and in addition to the investigations by vital staining mentioned, other studies have been made by Spemann (1912), Stockard (1913), Fischel (1921), and Bartelmez (1922), the last-mentioned working with human material. In the investigations reported here the method of vital staining has been employed. The main aim was the projection upon the neural plate of the most important areas of the fully developed brain. This led the author to the problem