ii8 THE PHYSIOLOGY OF REPRODUCTION 



Some of the deutobroque cells, instead of passing through the 

 transformations above described, rest for a time and subsequently 

 undergo retrogressive changes, becoming converted, according to 

 Miss Lane-Claypon, either into follicular epithelial cells or into 

 interstitial cells. " Every cell of the germinal epithelium is probably 

 a potential ovum, relatively very few remaining in the protobroque 

 state, although some may still be seen at the periphery in ovaries of 

 the eighteenth day [of gestation in the rabbit]. Incomparably the 





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FIG. 33. Ovary at birth, showing primordial follicles, x 300. 

 (From Williams' Obstetrics, Appleton & Co.) 



greater part pass into the deutobroque state, preparatory, doubtless, 

 to the formation of ova. All cannot become ova, for the other forms 

 of cell are necessary for the maintenance of the ovarian functions ; 

 possibly, therefore, only the most robust cells, and those which are 

 most conveniently situated for obtaining nourishment, undergo the 

 ovogenetic changes. This suggestion would seem to be borne out by 

 the fact that many more of the central cells, which are nearer the 



1909. For a general account of the egg and the phenomena of oogenesis in 

 the different groups of animals, both Vertebrate and Invertebrate, with a 

 complete bibliography, see Waldeyer, " Die Geschlechtszellen," in Hertwig's 

 Handbuch der Entwicklungslehre der Wirbeltiere, vol. i., Jena, 1903 ; also Wilson, 

 The Cell in Development and Inheritance, 2nd Edition, New York, 1900. 



