DESCRIPTION OF PLATES 



We wish to take this occasion to acknowledge our indebtedness to Mr. Royden 

 Hammond for all the photomicrographs, and to Mrs. Maud DeWitt Pearl for the 

 paintings on plate 9. 



PLATE 1 



EXPLANATION OF FIGURES 



1 Medium sized oocyte in hen ovary (X 40), showing three layers to the 

 follicle, the granulosa {g), theca interna ({), and theca externa (e), with nests 

 of lutear cells in the theca interna {I). 



2 Part of follicle wall in figure 1 at greater magnification (X 352). Labels 

 the same as in figure 1. 



18 



