. The development of the frog's egg; an introduction to experimental embryology. Embryology. Ch. VI] FORMATIOX OF THE GERM-LAYERS 65 with, the inner region of large 3-olk-cells. This ring of cells, as subsequent development shoivs, is the beginning of the embryo, and the ring itself is composed of the material which subsequently forms the central nervous system, the mesoderm, the notochord, and a part of the endoderm. An understanding of the subsequent development depends on a knowledge of the changes that take j)lace in this ring. The material of tlie rina: is intimately involved in the move-
. The development of the frog's egg; an introduction to experimental embryology. Embryology. Ch. VI] FORMATIOX OF THE GERM-LAYERS 65 with, the inner region of large 3-olk-cells. This ring of cells, as subsequent development shoivs, is the beginning of the embryo, and the ring itself is composed of the material which subsequently forms the central nervous system, the mesoderm, the notochord, and a part of the endoderm. An understanding of the subsequent development depends on a knowledge of the changes that take j)lace in this ring. The material of tlie rina: is intimately involved in the move- ments that take place during the overgrowth of the lower hemisphere by the lips of the blastopore. During this period, we must picture to ourselves the ring as rising up and draAving together over the lower white hemisphere, so that ultimately it leaves its equatorial position and its halves come together to form tlie embryo. (Fig. 24, A, B, C.). 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 Morgan, Thomas Hunt, 1866-1945. New York, The Macmillan company; [etc. , etc. ]
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectembryology, bookyear1
