358 B. F. KINGSBURY 



intermediate zone described above. Into the composition of the 

 zona parenchymatosa of the adult there goes, therefore, the defini- 

 tive cortex, the intermediate zone and a portion of the epitheho- 

 stromal nucleus. The zona vascularis is developed out of the 

 basal nucleus (connective tissue) of the growing ovary extended 

 at the expense of the epithelio-stromal nucleus, while the mar- 

 ginal growth of the ovary plays a part in establishing it. The 

 primitive medulla would include the epithelio-stromal nucleus 

 and the basal nucleus. 



The developmental changes that take place in the deeper por- 

 tions of the growing ovary, in the primitive medulla, are complex, 

 and this is intensified by the desirability of determining, for theo- 

 retical reasons, the exact mode of growth and the morphological 

 value at the different stages of the so-called medullary cords 

 which have so frequently been regarded as the equivalents of 

 the seminal tubules of the testis. The rete ovarii occupies a posi- 

 tion in the cephalic portion of the medulla (fig. 9). Its tubules 

 are, in the youngest embryo studied (75 mm.) easily distinguished, 

 of definite cuboidal-columnar epithelium, with a distinct lumen. 

 Subsequently, in older fetuses, the epitheliuni becomes more 

 distinctly flattened and the rete character more accentuated 

 (fig. 8). Whether the cell cords that form the structure are derived 

 from the mesothelium at the cephalic end of the ovary, or are 

 'ingrowths' from the mesonephros, or are of double origin and 

 nature, has not been made an object of investigation by me, and 

 hence of course cannot be adequately considered at this time. The 

 structure as observed in the growing organ suggests the last view. 

 The rete furthermore undergoes a progressive change after birth 

 and remains as a persistent structure in the adult ovary. It 

 requires no very extensive study of the ovary of older fetal and 

 new-born animals to determine that at least some of the medul- 

 lary cords are connected with the rete ovarii, as has been described 

 by others (von Winiwarter and Sainmont '08) and this requires 

 therefore no extended description or comment at this point. Two 

 other features of the medullary cords in the older embryos, the 

 presence of fat-granules in the cells, and the occurrence of large 

 cells within the cords, require brief discussion. Droplets of a 



