. The physical basis of heredity . Fig. 87.—A gynandromorph of Drosophiia melanogaster that was female on the right sideand male on the left. It was also yellow on the male side and gray on the normal side. SEX-CHEOMOSOMES AND INHERITANCE 191 character. It, or its normal allelomorph, should thereforebe present in both nuclei if all the chromosomes of thefertilized egg have divided normally except the X-chromo-somes. This, in fact, has been found to be the case (Mor-gan, Bridges, Sturtevant). Nearly all of the many hybrid gynandromorphs ofDrosophila can be explained as above. In a few cases,whe
. The physical basis of heredity . Fig. 87.—A gynandromorph of Drosophiia melanogaster that was female on the right sideand male on the left. It was also yellow on the male side and gray on the normal side. SEX-CHEOMOSOMES AND INHERITANCE 191 character. It, or its normal allelomorph, should thereforebe present in both nuclei if all the chromosomes of thefertilized egg have divided normally except the X-chromo-somes. This, in fact, has been found to be the case (Mor-gan, Bridges, Sturtevant). Nearly all of the many hybrid gynandromorphs ofDrosophila can be explained as above. In a few cases,when the abdomen of the fly was sufficiently female tomake mating possible, it has been found that the eggs givethe results expected for a female having the sex-linkedfactors that entered the Fia. 88.—Diagram showing elimination of X at an early cell-division, so that the nucleusto 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 ofthese cases can, however, be accounted for by anotherhypothesis. Should an egg arise with two nuclei (thereare several possible waj^s for this to occur), one nucleushaving one set of factors, the other the other set (theparent 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. Agynandromorph, described by Toyama, appears to belongto this category. Toyama found two gynandromorphsof the silkworm (Fig. 89) whose mother belonged to a racewith banded caterpillars, and whose father belonged to a 192 PHYSICAL BASIS OF HEEEDITY race with pale caterpillars. One of these was banded on theleft side (which side was also female) and pale on
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