MORPHOGENESIS OF THE MAMMALIAN OVARY 371 



ovary during the adult period are formed in the differentiation of 

 the cortical zone in the pre-sexual period. But one ovary (no. 

 39) was secured, clearly belonging to this period, in which the 

 primary follicles had nearly completely disappeared, giving the 

 picture described and figured by von Winiwarter and Sainmont. 

 This was, however, regarded as a case of exceptionally profound 

 degeneration, and showed no evidence of a renewed prolifera- 

 tion of oogonia from the surface epithelium. The margin of 

 the ovary bordering the hilum long (up to three months, at least) 

 remains a seat of proliferation and growth during the enlargement 

 of the ovary in the pre-sexual period, and it is quite possible that 

 in the second growth period (that immediately preceding sexual 

 maturit}^) following the period of profound degeneration and cor- 

 responding diminution in volume, the marginal surface epithe- 

 lium particularly resumes its proliferative activity with a result- 

 ing increase in the number of primary follicles. It is also quite 

 possible that the profound degeneration and consequent third 

 proliferation are related, and not constant but variable; only an 

 extreme morphological interpretation would reject the possibility. 

 The material, however, is insufficient for the settlement of these 

 points. Neither the preliminary paper of von Winiwarter and 

 Sainmont, nor the statements in their subsequent papers present 

 the evidence in a form that seems to me fully convincing, and the 

 promised chapter" upon the development of the third prolifera- 

 tion will be looked forward to with interest. 



If it is a matter of deep-seated importance and not a mere 

 expression of growth, a proUferation of ova just before sexual 

 maturity will be found to occur in other mammals. It may be 

 questioned, however, whether Rubaschkin ('12) is justified in 

 regarding what he terms a Hhird proliferation' from the surface 

 epithelium of the guinea pig ovary, occurring before birth, as 

 homologous with a (third) profiferation of ova just preceding 

 sexual maturity, such as von Winiwarter and Sainmont describe 

 for the cat. 



As a result of the profound degenerations before the onset of 

 sexual maturity there is left an ovary smaller but richer in stroma 



' See quotation, from p. 260, in footnote 0, p. 363. 



