MORPHOGENESIS OF THE MAMMALIAN OVARY 361 



with the testis. Such a comparison, to which the writer at first 

 incHned, seems to him upon maturer consideration a superficial 

 one. The elongated form, simulating a tubule is not the uni- 

 versal form of growth of these cell masses nor do they possess, 

 when elongated, the morphology of the seminal tubules."* The 

 form assumed is quite irregular and is obviously a factor of the 

 growth of the epithelial cords and stromal strands in their mutual 

 relation to one another in the growth of the ovary during this 

 period. 



The source of the cells that compose the cell cords and masses 

 so prominent during the period of expansion is also important in 

 this connection. Two modes of origin present themselves as 

 possible: (1) A development by centrifugal growth of the primary 

 medullary cords apparent in the embryo so that from them come 

 all the epithelial cords inside the zone of the primitive cortex. 

 This mode of growth would make the medullary structures a unit 

 and strengthen the ovary-testis comparison. (2) That the cords 

 and masses of epithelial cells within the medulla, while in many 

 instances connected with the prunary medullary cords and quite 

 possibly grown out from these cell groups, are nevertheless de- 

 rived in part from the indifferent cells contained in the egg cords 

 of the embryo. The differences of the epithelial cells would be 

 purely a matter of position and relation and not intrinsic or mor- 

 phological. 



It is this last view that seems to me undoubtedly the correct 

 one. Small groups of epithelial cells are to be found at all stages 

 of the postpartum growth in the central nucleus, the interme- 

 diate zone and, especially later, in the inner portion of the primi- 

 tive cortex. They are formed by the breaking up of the inner 

 portions of the egg cords into primary follicles. Many of these 

 primarj^ follicles and epithelial cell groups without an ovum en- 

 closed come to lie within the medulla, in the epithelio-stromal 

 nucleus where they subsequently grow and play a part in the de- 

 velopment of the medullary follicles, presently to be described. 



* Bremer, J. L. Amer. Jour. Anat., vol. 11, no. 4, May, 1911, pp. 393-416. Huber, 

 G. Carl, and Curtis G. M. Anat. Rec, vol. 7, no. 6, June, 1913, pp. 207-220. 



