Identifier: physicalbasisofhmorg (find matches)
Title: The physical basis of heredity
Year: 1919 (1910s)
Authors: Morgan, Thomas Hunt, 1866-1945
Subjects: Chromosomes Heredity Chromosomes Genetics, Medical
Publisher: Philadelphia London : Lippincott
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ous for a not sex-linked character, banded, andif she produced an e^g with two nuclei (Fig. 90). Don-caster has found such eggs in Abraxas, and has shownthat each nucleus extrudes separately polar bodies, andthat each reduced Qgg nucleus is fertilized by a separatespermatozoon. If as shown in the next diagram onereduced nucleus has a IF-chromosome, and a factor forbanded carried in one of the autosomes, and the otherreduced nucleus has a Z-chromosome, and in one of the SEX-CHROMOSOMES AND INHEEITANOE 193 autosomes a factor for pale, and if a spermatozoon, carry-ing the factor for pale, fertilizes each nucleus, the twozygotic nuclei will be ZW female and banded, and ZZmale and pale. This gives at least a formal explanationof the results, and helps us to see how such a rare event,the appearance of two gynandromorphs in the same brood,happened to occur at the same time; because, as Doncas-ters evidence shows, a double nuclear condition may becharacteristic of the eggs of certain females.
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Fia. 90.—Diagram illustrating how a heterozygous egg with two nuclei fertihzed by twosperms might produce a gynandromorph like that shown in Fig. 89. * Intersexes and Sex Gtenes The quantitative relation of one X for male and twoXs for female that has been found to hold in many of thegroups of animals might seem from a purely a prioripoint of view capable of being modified in such a way thatan intermediate condition might be realized, but whethersuch conditions should be expected to give rise to her-maphrodites or to non-sex-somethings (intermediates) —or to a mosaic of both sexes, or should rather be expectedto die could scarcely be foretold. There are three casesin which individuals called intersexes have been found,or produced; and since their interpretation has led to aview that has appeared to contradict the ordinary sex-determination scheme, these cases must be briefly referredto here. Goldschmidt has studied veiy thoroughly inter- 13 194 PHYSICAL BASIS OF HEREDITY sexes tha

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