Bennet Mills Allen 131 



that the granulosa cells are derived from the medullary cords. Xone 

 of the above named authors subjected this question to a critical study 

 of numerous stages in any species of animal; but studied isolated and 

 more or less mature stages. Wini-^'arter, oo, Balfour, 78, Coert, 98, 

 Nagel, 99, and many others hold, on the contrary, that the granulosa 

 cells arise from the cords of Pflliger. 



2. Medullary Cords. — The medullary cords which we found to be at 

 a standstill in development at the time of their separation from the peri- 

 toneum develop into structures in all regards similar to the cords of 

 Pfiiiger. Although homologous with the seminiferous tubules, they are 

 distinctly female in character. 



There is a constant degeneration of follicles in these medullary cords 

 and in the deeper portions of the cortex as well. This results in the 

 complete destruction of the sex cells in the former before the follicles 

 have developed far enough to possess more than a single layer of granu- 

 losa cells. The few such young follicles found in the medullary cords 

 and inner portions of the cords of Pfiiiger of the 13 cm. embryo, are 

 found to have disappeared in the 15 cm. stage, leaving small clumps of 

 more or less elongated granulosa cells enclosed in the membrana propria 

 and connective tissue investment that was previously formed about them. 

 These clumps remain throughout later stages, the persistent granulosa 

 cells taking on more or less the appearance of connective tissue. 



The fate of the medullary cords is quite similar in the rabbit. It will 

 be more explicitly dealt with in connection with the rete tubules. Suffice 

 it to say that the sex cells never pass beyond the stage of synapsis char- 

 acteristic of young oocytes in a certain early stage of development, the 

 few simple follicles that make their appearance lieing destined to degene- 

 rate as in the pig. 



3. Rete Tubides. — The subject of the rete tubules of the ovary is one 

 of the most interesting of the whole account. i\.s previously stated, they 

 contain primitive sex cells during the early stages in the development of 

 both male and female. These are present in both the extra- and intra- 

 ovarian portions. In that part of the rete lying within the sex gland, 

 they increase in number during the 4 cm. and 5 cm. stages of the pig, 

 becoming much more numerous than in that portion lying within the 

 mesonephros. The proximity of any given portion of the rete tissue 

 to the sex gland appears to condition the relative number of primitive 

 sex cells found in it. The rete tubules of the ovary are at all times 

 devoid of a lumen, and the intra-ovarian portions take on more and 

 more the appearance of the medullary cords and cords of Pflliger. This 

 similarity becomes very evident in the 13 cm. stage, at which period 



