. Text-book of embryology. Embryology. Fig. 22.—Portions of sagittal sections of Lepidosiren egg during early stages of gastrulation. A, showing process of delamination. The small-celled ectoderm is seen on the left: it is becoming extended by the addition, to its lower edge, of cells split off from the yolk-cells. The latter are recognizable by their larger size and by the larger size of the yolk-granules with which their cytoplasm is laden. B and C showing involution of the surface along the invagination-groove. processes are at work (1) Involution of the surface—this is conspicu- ous in the
. Text-book of embryology. Embryology. Fig. 22.—Portions of sagittal sections of Lepidosiren egg during early stages of gastrulation. A, showing process of delamination. The small-celled ectoderm is seen on the left: it is becoming extended by the addition, to its lower edge, of cells split off from the yolk-cells. The latter are recognizable by their larger size and by the larger size of the yolk-granules with which their cytoplasm is laden. B and C showing involution of the surface along the invagination-groove. processes are at work (1) Involution of the surface—this is conspicu- ous in the first stages (see Fig. 22, B and C), (2) Overgrowth by the gastrular lip—the " dorsal" lip as it is commonly termed from its ultimate position, and (3) Delamination. These same three factors are at work in the gastrulation of the lower Vertebrates in general, and a clear realizing of their nature is necessary to a comprehension. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original MacBride, E. W. (Ernest William), 1866-1940; Kerr, John Graham, 1869-; Heape, Walter, 1855-1929. London : Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
