PLATE 4 



EXPLANATION" OF FIGURES 



37 Stage 'c'. This oocyte was surrounded by a follicle of flattened cells 

 and was partly in the tunica albuginea beneath. Same ovary as figure 28. 

 (Eleven days p.p., P.A.F., I.H.) 



38 Stage 'c'. Follicle formation. The free surface of the epithelium is 

 toward the left. Same ovary as figure 37. 



39 Stage 'c'. This oocyte was in a follicle of flattened cells, under the epithe- 

 limn and surrounded by the connective tissue cells of the tunica albuginea. Same 

 ovary as figure 37. 



40 Stage 'c'. Primary oocyte in follicle just untler the germinal epithelium. 

 Mouse twenty-eight days p.p. FL, Tri. 



41 Oocyte in primary follicle of flattened cells. Mouse sexually mature 

 (ninety days p.p.). Carnoy's, I.H. 



42 Stage 'c'. Oocyte in primary follicle of cuboidal cells. Mouse sexually 

 mature (sixty-seven days p.p.). FL, I.H. 



43 Stage 'c'. Oocyte in follicle of tall cuboidal cells which are in two layers 

 in places. Same ovary as figure 42. 



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