THE DEVELOPMENT OF THE UROGENITAL SYSTEM. 435 



and testicles, true hermaphroditism is the result; if they give rise to either 

 ovaries or testicles but the external genitalia and general characteristics develop 

 in the opposite direction, false hermaphroditism is the result. Thus the her- 

 maphroditic condition is potentially present in every individual during the 

 earlier stages of development; the most remarkable fact is that it is not more 

 common. 



Recent researches in cytology have added a new phase to the question of the 

 origin of hermaphroditism. Accessory chromosomes have been demonstrated 

 in the ova and spermatozoa of many species of insects (McClung, Wilson, 

 Morgan) and in ova and pollen of dioecious plants (Correns). It has been 

 suggested that these have some significance in the determination of sex, the 

 female elements containing the additional chromatin elements (see p. 27). 

 Carrying this a step further, Adami has suggested that " hermaphroditism is 

 based upon aberration in the distribution of the chromosomes in either the ovum, 

 or the spermatozoon." 



References for Further Study. 



ADAMI, J. G.: The Principles of Pathology. Vol. I, 1908. 



AICHEL, O.: Vergleichende Entwickelungsgeschichte und Stammesgeschichte der 

 Nebennieren. Arch. f. mik. Anat.. Bd. LVL, 190x5. 



ALLEN, B. M.: The Embryonic Development of the Ovary and Testis in Mammals. 

 Am. Jour, of Anat., Vol. Ill, 1904. 



BEARD, J.: The Germ-cells of Prisdurus. Anat. Anz., Bd. XXI, 1902. 



BEARD, J.: The Morphological Continuity of the Germ Cells in Raja batis. Anat. Anz., 

 Bd. XVIII, 1900. 



BONNET, R.: Lehrbuch der Entwickelungsgeschichte. Berlin, 1907. 



EIGENMANN, C. H.: On the Precocious Segregation of the Sex-cells of Micrometrus 

 aggregatus. Jour of Morphol., Vol. V, 1891. 



FELIX, W.: Entwickelungsgeschichte des Excretions-systems. Ergebnisse der Anat. 

 u. Entwick., Bd. XIII, 1903. 



FELIX, W., and BUHLER^ A.: Die Entwickelung der Harn- und Geschlechtsorgane. In 

 Hert wig's Handbuch d. vergleich. u. experiment. Entwickelungslehre der Wirbeltiere, Bd. III. 

 Teil I, 1904. 



GAGE, S. P.: A Three Weeks' Human Embryo, with Especial Reference to the Brain and 

 Nephric System. Am. Jour, of Anat., Vol. IV, 1905. 



GERHARDT, U.: Zur Entwickelung der bleibenden Nieren. Arch. f. mik. Anat , Bd 

 ILVII, 1901 



HERTWIG, O.: Lehrbuch der Entwickelungsgeschichte des Menschen und der Wirbel- 

 tiere. Jena, 1906. 



HILL, E. C.: On the Gross Development and Vascularization of the Testis. Am. 

 Jour. of. Anat., Vol. VI, 1907. 



HUBER, G. C.: On the Development and Shape of the Uriniferous Tubules of Certain 

 of the Higher Mammals. Am. Jour, of Anat., Vol. IV, Suppl., 1905. 



KEIBEL, F.: Zur Entwickelungsgeschichte des menschlichen Urogenitalapparatus. 

 Arch.f. Anat. u. Physiol., Anat. Abth. y 1896. 



KOHN, A.: Das chromaffine Gewebe. Ergebnisse der Anat. u. Entwick., Bd. XII, 1903, 



