. The physical basis of heredity . Heredity. 202 PHYSICAL BASIS OF HEREDITY females {XXX) that die, and (4) red-eyed males (XY). The last are exceptional, since white-eyed females nor- mally never produce anything but white-eyed sons. Here the exceptional male is due to an egg without an X, being fertilized by a "female-producing" (or Z-bearing) sperm. The three X individuals have never been found, and undoubtedly die, presumably from too many X's. The remaining red females are of two kinds, one normal XX POLAH BODY EGGS SPERM. WHITE d s WHITE d 6 WHITE 9 (^EPT'ON) 7 DIES Fig. 94.âNo
. The physical basis of heredity . Heredity. 202 PHYSICAL BASIS OF HEREDITY females {XXX) that die, and (4) red-eyed males (XY). The last are exceptional, since white-eyed females nor- mally never produce anything but white-eyed sons. Here the exceptional male is due to an egg without an X, being fertilized by a "female-producing" (or Z-bearing) sperm. The three X individuals have never been found, and undoubtedly die, presumably from too many X's. The remaining red females are of two kinds, one normal XX POLAH BODY EGGS SPERM. WHITE d s WHITE d 6 WHITE 9 (^EPT'ON) 7 DIES Fig. 94.âNon-disjunction. In the upper part of the figure the four poBsible modes of elimination of the sex-chromoaome from the XXY eggs are shown, and the results of their fertilization by a Y-bearing sperm of the male is shown below. and the other (XXY), which is expected to repeat the exceptional behavior of her mother. In fact, this is what she does. In the next diagram (Fig. 94) the fate of the same four kinds of eggs is shown if they are fertilized by a Z-bearing sperm. Four classes of individuals are expected (5) white males (XYY) â (6) white males (XY); (7) white females (XXY); and (8) YY individuals. No individuals having the last make-up have ever been found, and there can be no doubt that an individual without at least one X dies. The white-eyed females are exceptional, since white-eyed. 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. Philadelphia : Lippincott
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