File:Heredity and sex (1913) (14764536162).jpg

Identifier: hereditysex00morg (find matches)
Title: Heredity and sex
Year: 1913 (1910s)
Authors: Morgan, Thomas Hunt, 1866-1945
Subjects: Heredity Sex
Publisher: New York, N.Y. : Columbia University Press
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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part of the bodymale organs develop, and in another part a femalesystem ? Two views suggest themselves, either somatic segre-gation, or regional differentiation. By somatic seg-regation I mean that at some time in the developmentof the embryo — at some critical division — a separa-tion of chromosomes takes place so that an egg-produc-ing group and a sperm-producing group is formed.There is no direct evidence in support of this view. Another view is that the formation of ovary andtestis is brought about in the same way as alldifferentiations of body organs, as for example the 168 HEREDITY AND SEX formation of liver and lungs and pancreas from thedigestive tract. The following case may perhapsbe considered as supporting such an hypothesis. Ina hermaphroditic worm, Criodrilus lacuum the ovarieslie in the thirteenth and the testes in the tenth andeleventh segments. If the anterior end be cut off, anew one regenerates, as shown by Janda (Fig. 85), Fig. 1, Fig. 2. -Kg. 3. Fig. 4. Pig. 6
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Fig. 85. — 1, anterior end of normal criodrilus, showing reproductivesystem; 2-5, regenerated anterior ends. (After Janda.) in which the ovaries and testes reappear approximatelyin their appropriate regions. It is true their locationis more liable to vary than in the normal worm, butthis is unimportant. The important point is thatthey must be produced from parts of the body thathave never produced them before, and it is unlikelytherefore that any preparation for this casualty wouldhave been made. The location and differentiation HERIVIAPHRODITISM 169 of these organs may seem to depend on the samerelation-of-the-parts-to-each-other on which allsomatic differentiation depends. If this were the correct interpretation then the prob-lem of sex in hermaphrodites would appear in a differentlight from the problem of sex in species in which malesand females occur, and the appeal would be made to anentirely different principle. In cases where a sexual generation alternates witha hermaphroditi

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