356 B. F. KINGSBURY 



definitive cortex. In the deeper portions of the ovary marked 

 growth activity of the stroma introduces a complexity not en- 

 countered in the typical zone of the primitive cortex. In the 

 ovary before birth and for the first few days after birth the egg 

 cords, project deeply into the ovary, occupying a position which 

 subsequently will become medulla. The egg cords are typically 

 branched, presenting the characteristic appearance well known 

 from previous published descriptions by several workers (figs. 8-9) . 

 In the deeper portions of the egg cords the ova are the most ad- 

 vanced in development and both types of cells — egg cell and 

 follicle cell — may be recognized in this portion of the egg cord. 

 The surrounding stroma is relatively denser in this middle zone 

 of the ovary and the growth activity of the stroma appears par- 

 ticularly marked here. The strands of stroma cells run irregu- 

 larly, some having a more radial, others a more tangential direc- 

 tion. 



Because of the presence of egg cords in this zone, it is usually 

 grouped as part of the primitive cortex. It might with equal 

 propriety be regarded as part of the medulla, since medullary 

 ■cords are also contained therein — that is, groupings of mainly 

 indifferent cells with only an occasional definite ovum. This 

 zone is in fact an intermediate zone and its peripheral portion 

 persists as a boundary zone during the period of postnatal growth 

 of the ovary. 



In their deeper portions the egg cords become separated into 

 cell groups containing one or more ova and in this way numerous 

 follicles are formed. Then- number appears to be added to by 

 continued 'cutting off' of egg cells from the egg cords in the inter- 

 mediate zone. In this zone of the postnatal ovary great com- 

 plexity exists. It seems to represent the main line of advancing 

 stromal growth following upon the peripheral (and superficial) 

 zone of epithelial proliferation, perhaps associated with the be- 

 ginning follicular differentiation. 



In illustration of the more general features of the morphogen- 

 esis, figures 8 to 15 may be consulted. The distinctness of the 

 cortex becomes progressively more marked until it assumes its 

 definitive structure. This applies as well to the other zones of 



