Archive image from page 6 of The development of the mesonephras. The development of the mesonephras and the Müllerian duct in Amphibia . developmentofmes00hall Year: 1904 hall: mesonephros and mullerian duct in amphibia. 33 primitive coelom. 'While ventrally the coelom is uninterrupted, dorsally it exists in the shape of separate pockets, so that the mesoderm has the form of separate, hollow processes whose median walls are composed of splanchnoderm, the lateral walls of somatoderm. These processes are the somites. A diagrammatic cross-section of one is shown in Figure A. They seem to be rep
Archive image from page 6 of The development of the mesonephras. The development of the mesonephras and the Müllerian duct in Amphibia . developmentofmes00hall Year: 1904 hall: mesonephros and mullerian duct in amphibia. 33 primitive coelom. 'While ventrally the coelom is uninterrupted, dorsally it exists in the shape of separate pockets, so that the mesoderm has the form of separate, hollow processes whose median walls are composed of splanchnoderm, the lateral walls of somatoderm. These processes are the somites. A diagrammatic cross-section of one is shown in Figure A. They seem to be represented in their most primitive condition in the elasmobranchs, where, according to Van Wyhe ('89), the seg- mentation extends ventrad even through the region of the germinal epitheliurn. Three regions may be more or less distinctly recognized met: TTis'mer. â K0) Figures A-D. Four figures to illustrate the relation of the mesomer to the rest of the mesoderm. For explanation see Introduction (page 32). The median plane of the body is at the right in each case. in each somite. The most dorsal, to adopt the nomenclature of Van Wyhe, is the epimer (earner., Fig. A), generally designated as the myotome because the main trunk-muscles are derived from it. Its cavity is the epicoelom. Passing ventrad, the next region is the mesomer (ins''mei\\ enclosing the mesocoelom. The mesomer has been designated by the terms middle plate, intermediary cell-mass, 'Urwirbelkommunikation,' etc. The sclerotome may be considered as arising from the upper por- tion of its median wall, but the major part of both walls seems to enter into the formation of the nephric fundaments. For this reason
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