268 H. M. KINGERY 



layers of cuboidal cells and fill up the interior of the ovary^ 

 constituting the bulk of it (fig. 12), Clearly marked off from 

 these is a superficial layer of egg-cells two to five deep, in primary 

 follicles, made up of a single layer of flattened cells. The large 

 central egg-cells with their follicles are those which have arisen 

 by the proliferation of cells from the germinal epithelium before 

 birth, as described above; the oocytes in the primary follicles 

 have been formed from the epithelium by a proliferation begin- 

 ning about birth or shortly after — a process to be described below. 

 Cavities begin to appear in the larger follicles between fifteen 

 and eighteen days post partum, and a degeneration of the egg- 

 cells sets in at about the same time. The evidence shows that 

 all these germ cells formed before birth degenerate and are 

 resorbed, none of them developing into definitive ova. This 

 degeneration takes the form of atrophy and resorbtion in some 

 cases, but in others there may occur atresia folliculi, accompanied 

 by the formation of a first polar body and a degenerative frag- 

 mentation of the egg-cell, simulating more or less closely a 

 parthenogenetic cleavage (Kingery, '14). • 



During the early development of the ovary the cells of the 

 germinal epithelium vary in shape from rather tall cuboidal to 

 somewhat flattened cells, a large number being more or less 

 rounded. The nuclei are large, nearly filling the cell, and the 

 cytoplasm is scant in amount. After birth certain of these 

 cells begin their development into oocytes. They begin to grow 

 and enlarge in situ in the epithehum. At first more or less 

 spherical, as they become larger than the other cells of the 

 epithelium they project from the surface of the ovary. These 

 small protuberances are very noticeable between three and thirty 

 days after birth (figs. 35, 36, 38, 1 to 3.) These cells soon become 

 oval, however, with their long axes tangential to the surface of 

 the ovary. As they enlarge, the adjacent epithelial cells are 

 crowded to either side (or end) and are flattened against and 

 around the egg-cells (figs. 35, 36.) As the egg-cells grow still 

 larger, the bulging on the surface becomes more marked. In 

 the course of further development some of these flattened cells 

 extend up over (outside of) and under (inside of) the oocyte so 



