. Embryology. Embryology; Embryology; genealogy. SINGLE EMBRYO FORMS FUSION OF TWO EGGS Fig. 4. Action begins at left of diagram. Two fertilized amphibian eggs, AB, CD, are placed side by side. Each egg then divides once, forming two two- cell eggs. One two-cell egg, CD, is rotated through 90° and placed on top of the other, AB, with the result that ABCD stick together. The fused eggs continue to develop and form a single embryo. What sort of structure must the eggs AB and CD possess in order that they may fuse and form only one embryo ? and, as a matter of fact, the parts of an egg can be int
. Embryology. Embryology; Embryology; genealogy. SINGLE EMBRYO FORMS FUSION OF TWO EGGS Fig. 4. Action begins at left of diagram. Two fertilized amphibian eggs, AB, CD, are placed side by side. Each egg then divides once, forming two two- cell eggs. One two-cell egg, CD, is rotated through 90° and placed on top of the other, AB, with the result that ABCD stick together. The fused eggs continue to develop and form a single embryo. What sort of structure must the eggs AB and CD possess in order that they may fuse and form only one embryo ? and, as a matter of fact, the parts of an egg can be interchanged without any resultant abnormalities in development. For example, in an early stage of development of the amphibian egg—it is important that it be an early stage—it is possible to interchange pieces of the egg destined to be- come skin with pieces destined to become the nervous system. The adult skin is one type of structure; the adult nervous tissue quite another. But they can be interchanged in an early stage. Figure 5 shows two eggs. A piece of the future skin is cut from one egg and interchanged with a piece of the future brain of the other egg. Later the part that was originally destined to be skin can be recognized as a part of the primitive nervous system of the embryo which received it. In its new position it forms a fairly normal part of the nervous system. And if it comes from the same species it forms a perfect nervous system. In Figure 5 the skin which became nervous tissue looks different because it came from a different species. The use of two different species was intentional in order to show very clearly the part which was originally transplanted. Thus, cells normally destined to form skin can become nervous tissue, nerve fibers, and. 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 wor
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Keywords: ., boo, bookcentury1900, booksubjectembryology, booksubjectgenealogy
