68 



THE VERTEBRATE OVARY AND ITS RELATIONSHIP TO REPRODUCTION 



2. Position Occupied by the Primitive Female Germ Cells 

 IN THE Ovarian Cortex 



Within the cortex the definitive germ cells or oogonia are found in or near 

 the germinal epithelium (figs. 39, 64). Some authors regard the oogonium 

 as originating from the cells of the germinal epithelium. (See Chap. 3, section 

 on "germ cell origin.") The definitive germ cell soon becomes associated 

 with small epithelial cells (fig. 41). This complex of a germ cell with its 

 associated epithelial cells is found somewhat deeper in the cortex, within or 

 below the tunica albuginea. As the oogonium begins to experience the changes 

 propelling it toward a state of maturity, it is regarded as an oocyte (Chap. 3). 

 Characteristics of the primitive oocyte are: 



(1) an enlargement of the nucleus, 



(2) changes within the chromatin material of the nucleus pertaining to 

 meiosis (Chap. 3), and 



(3) a growth and increase in the cytoplasmic substances (fig. 41). 



PROLIFERATING 



GERM CELL 





Fig. 39. (A) Diagrammatic representation of portion of the cortex of a young opossum 

 ovary near the hiius, showing origin of germ ceils from germinal epithelium or from 

 cells lying in or near the germinal epithelium of the ovary. (After Nelsen and Swain, 

 J. Morphol., 71.) (B) Young oocytes in rat ovary, lying in or near the germinal epi- 

 thelium of the ovary. (After Jones. J. Morphol., 84.) 



