Heredity and sex . Fig. 86. —Rhabditis nigrivernjsa, male (left) and female (right). (After Leunis.) ^ sexes reappears. There is but one case in animalsthat has been adequately worked out. A nematodeworm, Rhahditis nigrovenosa, hves as a parasite inthe lungs of frogs. It is an hermaphrodite. Itseggs give rise to another generation that hves in mudand slmie. In this generation two kinds of individualsare present — true males and females (Fig. 86). Thefemales produce eggs, that are fertihzed, and develop 170 HEREDITY AND SEX into the hermaphrodites which find their way againinto the lungs of fro
Heredity and sex . Fig. 86. —Rhabditis nigrivernjsa, male (left) and female (right). (After Leunis.) ^ sexes reappears. There is but one case in animalsthat has been adequately worked out. A nematodeworm, Rhahditis nigrovenosa, hves as a parasite inthe lungs of frogs. It is an hermaphrodite. Itseggs give rise to another generation that hves in mudand slmie. In this generation two kinds of individualsare present — true males and females (Fig. 86). Thefemales produce eggs, that are fertihzed, and develop 170 HEREDITY AND SEX into the hermaphrodites which find their way againinto the lungs of frogs. Boveri and Schleip have worked out the historyof the chromosomes in this case. The cells of the X---h-. FiG. 87. — Chromosomes of Angiostomum. (A), oogonia; (B), equa-torial plate of first maturation division; (C), young spermatocyte;(D), first spermatocyte division in metaphase; (E), same in anaphase;(F), spermatocyte of second division; (G), and (H), division of same;(7), and (K), loss of X at plane of division ; (L), first segmentation divisionof a male embryo ; two sets of chromosomes (5 and 6=11 respectively)separate; (M) equatorial plate of dividing cell of female embryo = 12chromosomes; (N), same from male embryo =11 chromosomes. (AfterSchleip.) hermaphrodite have twelve chromosomes (Fig. 87).The eggs, after extruding two polar bodies, havesix chromosomes. The spermatozoa that developin the body of the same animal have six or five chro-mosomes each, because one chromosome is lost in half HERMAPHRODITISM 171 of the cells by being left at the dividing line betweenthe two cells. We can understand how two kindsof individuals are produced by the hermaphroditesfrom the two classes of
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
