. The physical basis of heredity . Heredity. SEX-CHROMOSOMES AND INHERITANCE 191 character. It, or its normal allelomorph, should therefore be present in both nuclei if all the chromosomes of the fertilized egg have divided normally except the Z-chromo- somes. This, in fact, has been found to be the case (Mor- gan, Bridges, Sturtevant). Nearly all of the many hybrid gynandromorphs of Drosophila can be explained as above. In a few cases, when the abdomen of the fly was sufficiently female to make mating possible, it has been found that the eggs give the results expected for a female having the
. The physical basis of heredity . Heredity. SEX-CHROMOSOMES AND INHERITANCE 191 character. It, or its normal allelomorph, should therefore be present in both nuclei if all the chromosomes of the fertilized egg have divided normally except the Z-chromo- somes. This, in fact, has been found to be the case (Mor- gan, Bridges, Sturtevant). Nearly all of the many hybrid gynandromorphs of Drosophila can be explained as above. In a few cases, when the abdomen of the fly was sufficiently female to make mating possible, it has been found that the eggs give the results expected for a female having the sex-linked factors that entered the FiQ. 88.—Diagram showing elimination of X' at an early cell-diviaion, so that the nucleus to the right gets X and X' and that to the left only X. In a few cases in Drosophila the explanation of chro- mosomal dislocation will not cover the results. Some of these cases can, however, be accounted for by another hypothesis. Should an egg arise with two nuclei (there are several possible ways for this to occur), one nucleus having one set of factors, the other the other set (the parent being heterozygous), then if each nucleus is sepa- rately fertilized a different combination of factors is pos- sible from that possible on the elimination theory. A gynandromorph, described by Toyama, appears to belong to this category. Toyama found two gynandromorphs of the silkworm (Fig. 89) whose mother belonged to a race with banded caterpillars, and whose father belonged to a. 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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