Heredity and sex . FiG. 111. — Nine-banded Armadillo. Four identical twins with acommon placenta. (After Newman and Patterson.) duced (Fig. 112). The material out of which theydevelop separates from the rest of the embryonictissue at a very early stage. The four embryos areidentical quadruplets in the sense that they are morelike each other than like the embryos of any otherlitter, or even more like each other than they are totheir own mother. The second source of evidence concerning sex-deter- SPECIAL CASES OF SEX-INHERITANCE 239 mination in man is found in the heredity of sex-hnkedcharacters
Heredity and sex . FiG. 111. — Nine-banded Armadillo. Four identical twins with acommon placenta. (After Newman and Patterson.) duced (Fig. 112). The material out of which theydevelop separates from the rest of the embryonictissue at a very early stage. The four embryos areidentical quadruplets in the sense that they are morelike each other than like the embryos of any otherlitter, or even more like each other than they are totheir own mother. The second source of evidence concerning sex-deter- SPECIAL CASES OF SEX-INHERITANCE 239 mination in man is found in the heredity of sex-hnkedcharacters. The following cases may well serve to illustratesome of the better ascertained characters. The tablesare taken from Davenports book on Heredity inRelation to Eugenics. The squares indicate males,affected males are black squares ; the heavy circles indi-cate females, that are supposed to carry the factors, but. Fig. 112. — Nine banded Armadillo. Embryonic blastocyst that hasfour embryos on it, two of which are seen in figure. (After Newman andPatterson.) such females do not exhibit the character black circles stand for affected females. Haemophilia appears in affected stocks almost ex-clusively in males (Fig. 113). Such males, matingwith normal females, give only normal offspring, butthe daughters of such unions if they marry normalmales will transmit the disease to half of their females can arise only when a hsemophiliousmale marries a female carrying haemophilia. If we 540 HEREDITY AND SEX
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
