824 



THE REPRODUCTIVE ORGANS 



[CH. LVIII. 



It has been suggested that the corpus luteum yields an internal 

 secretion, the effect of which is to assist gestation in some at present 

 unknown way. 



Many of the Graafian follicles never burst; they attain a 



Nucleus or germinal vesicle. 

 Nucleolus or germinal spot. 



Space left by retraction of 

 protoplasm. 



Protoplasm containing yolk 

 spherules. 



Zona pellucida. 



FIG. 617. A human ovum. (Cadiat.) 



certain degree of maturity even during childhood, then atrophy 

 and disappear. 



The ovarian ovum or oocyte of the first order (fig. 617) is a large 



FIG. 618. Diagram showing mode of development of oocytes of the first order from primitive germ cells 

 in mammalian ovary. 1, germinal epithelium ; 2, primitive germ cells ; 3, oogonia ; 4, oocytes of 

 the first order. In A, two primitive germ cells are seen imbedded in the germinal epithelium. In 

 B, a primitive germ cell has descended into the stroma of the ovary accompanied by cells proliferated 

 from the germinal epithelium which will become the cells of the membrana granulosa. In C, the 

 oogonia derived from primitive germ cells, and oocytes of the first order produced by division of the 

 oogonia, are seen. (After Buhler.) 



spheroidal cell surrounded by a transparent striated membrane called 

 the zona pellucida, or zona striata. The protoplasm is filled with large 



