Beunet Mills Allen 139 



as it again thins out and loecomes relatively unimportant in later stages. 

 In any case, there is a remarkably close correspondence between the gen- 

 eral processes of development of the testis and ovary. 



I wish to express my deep obligations to my professor. Dr. Frank K. 

 Lillie, for constant guidance and valuable assistance throughout the 

 course of this work. 



VI. SUMMARY AND CONCLUSIONS. 



1. The sex glands and rete originate from the genital ridge composed 

 of the thickened mesonephric peritoneum and underlying tissue, pro- 

 liferated from it. 



2. The testis is composed of (A) the seminiferous tubules, (B) stroma. 



A. The seminiferous tubules are formed as solid invaginations of the 

 peritoneum, which later became separated from it, and undergo subse- 

 quent growth by the activity of the component cells. These are of two 

 kinds, (1) primitive sex cells, spermatogonia of the second order; and 

 (2) germinative cells. Intermediate forms connect these two kinds and 

 may be interpreted as the primitive cells from which both varieties origi- 

 rate. They occur' up to a certain stage in development, and may possi- 

 bly recur periodically in adult stages. 



B. The stroma consists of (1) loose connective tissue, (2) the albu- 

 ginea — formed from the cells comprising the proximal portions of the 

 seminiferous tubules together with possible additions of other connective 

 tissue from the stroma, (3) interstitial cells formed from the stroma. 

 These are formed contemporaneously with the appearance of fatty de- 

 generation in both peritoneum and seminiferous tubules. 



3. The ovary is made up of homologous groups of structures. 



A. The medullary cords and cords of Pfliiger are both derived by 

 invagination of the peritoneum, the former being in all regards homo- 

 logous with the seminiferous tubules. The cords of Pfliiger are invagina- 

 tions of the peritoneum, formed after the medullary cords have become 

 separated from it. Both medullary cords and cords of Pfliiger contain 

 oogonia and follicle cells. Follicles formed in the medullary cords are 

 never functional and cease to form in later stages. They degenerate 

 together with other young follicles of the inner ends of the cords of 

 Pfliiger. Both medullary cords and cords of Pfliiger contain (1) primi- 

 tive sex cells (oogonia) ; (2) follicular cells — probably homologous with 

 the germinative cells of the seminiferous tubules; while intermediate 

 forms of cells are found in the peripheral part of the ovary. 



B. The stroma consists of (1) loose connective tissue, from which are 

 derived the theca interna and theca externa of tlie follicles; (2) a zone 



