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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rowth period ; 4-7, prophases ;8, equatorial plate of first division, 9-10 ; 11, spermatocytes of second order ;12-13, division of same; 14-16, the four cells or spermatids that comefrom the same original cell, two with 5, two with 6 chromosomes; 17,spermatids; 18, mature sperm; 19, living sperm. (After Mulsow.) In these insects a study of the chromosomes showsthat the male has one less chromosome than the female.At the first maturation division in the male (Fig. 30),all the chromosomes divide except one, the X chromo-some, and this passes to one cell only. This cell isalso larger than the sister cell. The small cell lackingthe X degenerates, and does not produce spermato- THE MECHANISM OF SEX-DETERMINATION 53 zoa. The large cell divides again, all of the chromo-somes dividing. Two functional spermatozoa areproduced, each carrying one sex chromosome. Thesespermatozoa correspond to the female-producing sper-matozoa of other insects. In the sexual female there is an even number of chro-
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