888 



THE DEVELOPING ENDOCRINE GLANDS 



Fig. 368. The sex chromosomes in man, opossum, chick, and Drosophila; parabiotic 

 experiments in Amphibia. (A) Late primary spermatocyte in human. (A') First 

 maturation spindle in human spermatocyte. (Redrawn from Painter, '23, J. Exper. Zool., 

 37.) (B) Dividing spermatogonium in opossum testis. (B') First maturation spindle 

 in spermatocyte of opossum. (Redrawn from Painter, '22, J. Exper. Zool., 35.) (C) 

 Sex chromosomes in female Drosophila. (C) Sex chromosomes in male Drosophila. 

 (Redrawn from Morgan, Embryology and Genetics, 1934, Columbia University Press, 

 N. Y., after Dobzhansky. ) (D) Sex chromosomes in common fowl, male. (D') Sex 

 chromosomes in common fowl, female. (Redrawn from Bridges, 1939, Chap. 3, Sex and 

 Internal Secretions, edited by Allen et al., Baltimore, Williams and Wilkins, after Sokolow, 

 Tiniakow, and Trofimov. ) (E-G) Diagrams illustrating the spreading of gonadal sub- 

 stances in frogs, toads, and salamanders. In toads, E, the gonadal influences (antagonisms) 

 are evident only when the gonads actually are in contact. In the frogs, F, the range of 

 influence is wider but its effect falls off peripherally. Figure G represents the condition 

 in newts and salamanders. It is evident that in this group, some substance is carried in 

 the blood stream which suppresses the gonads in the two females as indicated in the 

 diagram. (Redrawn and modified slightly from Witschi, 1939, Chap. 4, Sex and Internal 

 Secretions, edited by Allen et al., Baltimore, Williams and Wilkins.) 



somes is present the developmental forces swing in the direction of the 

 female sex. Sex, from this point of view, is determined by a genie balance, a 

 balance which in turn is governed by the quality of certain genes as well as 

 the quantitative presence of genes. (For detailed discussion consult Bridges, 

 '39, and White, '48.) 



