. Heredity in relation to evolution and animal breeding, . Heredity. HEREDITY. Fig. 2. — Fertilization of the egg of Nereis. A. The sperm has entered the egg and is forming a minute nucleus at o*. The egg-nucleus is breaking up preparatory to the first maturation division. B. The egg-nucleus is undergoing the first maturation division. Notice the con- spicuous rod-like chromosomes separating into two groups. The sperm-nucleus (,J) is now larger and lies deeper in the egg. C. A small polar-cell has been formed above by the first maturation division of the egg. A second division is in progress a
. Heredity in relation to evolution and animal breeding, . Heredity. HEREDITY. Fig. 2. — Fertilization of the egg of Nereis. A. The sperm has entered the egg and is forming a minute nucleus at o*. The egg-nucleus is breaking up preparatory to the first maturation division. B. The egg-nucleus is undergoing the first maturation division. Notice the con- spicuous rod-like chromosomes separating into two groups. The sperm-nucleus (,J) is now larger and lies deeper in the egg. C. A small polar-cell has been formed above by the first maturation division of the egg. A second division is in progress at the same point. The sperm-nucleus is now deep in the egg and is preceded by a double radiation (am- phiaster). Z). Two polar-cells are fully formed. The ma- tured egg-nucleus is now fusing with the sperm-nucleus. An amphiaster indicates that division of the egg will soon take place. (After Wilson.) 1?. 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 Castle, William E. (William Ernest), 1867-1962. New York ; London : D. Appleton and Company
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