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Derivatives of the Primary Germ Layers

Gastrulation is a critical stage in the development of any embryo. This is due in part to the fact that the positional relationship of the various cells of the late blastula and early gastrula begins to take on special significance. This has been demonstrated by many experimental embryologists, among whom are His, Born, BUtschli, Rhumbler, Spek, Vogt, Dalcq, Pasteels, Vintemberger, Holtfreter, Nicholas, and Schechtman. They have used various experimental devices, such as injury or excision of cell areas, or staining local areas with vital dyes and following their subsequent movement. By such methods the socalled "fate maps" of various blastulae have been worked out.

A fate map is simply a topographical surface mapping of the blastula with respect to the ultimate fate of the various areas. When one traces a cell group on the surface of a blastula which has been vitally stained with Nile blue sulfate, for instance, and finds that these cells move from the marginal zone (between the animal and the vegetal hemispheres) over the dorsal lip of the early blastopore and into the embryo where they become pharyngeal endoderm, he is then able to label the fate of that area on other blastulae. The fate maps of various amphibia are basically alike, but they are not sufficiently alike in detail to permit plotting a universal amphibian fate map. The frog's egg is very dark and it is difficult to apply vital dyes so that they will be visible on the frog blastula. However, the fate maps of closely related species have been worked out and, combined with circumstantial experimental evidence on the frog's egg, we are able to supply what is believed to be a reasonably accurate fate map of the frog blastula.


Courtesy, Patten: "Embryology of the Pig", Philadelphia, The Blakiston Company. 1927

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)
Frog Development (1951): 1 Introduction | 2 Rana pipiens | 3 Reproductive System | 4 Fertilization | 5 Cleavage | 6 Blastulation | 7 Gastrulation | 8 Neurulation | 9 Early Embryo Changes | 10 Later Embryo or Larva | 11 Ectodermal Derivatives | 12 Endodermal Derivatives | 13 Mesodermal Derivatives | 14 Summary of Organ Appearance | 15 Glossary | 16 Bibliography | Figures


Rugh R. Book - The Frog Its Reproduction and Development. (1951) The Blakiston Company.

Cite this page: Hill, M.A. (2024, April 25) Embryology Rugh 063.jpg. Retrieved from

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