DEVELOPMENT OF REPRODUCTIVE SYSTEM 793 



a Straightened condition and project inward toward the area connect- 

 ing the sex gland with the mesonephric kidney (fig. 350D). 



(4) In the area between the inner ends of the developing seminiferous 

 tubules and the Malpighian corpuscles of the mesonephric tubules, a 

 condensation of cellular material occurs which forms the rete primor- 

 dium (fig. 350D). From the rete primordium the future rete tubules 

 are developed. 



(5) As the rete tubules form, they unite with the inner straightened por- 

 tions of the seminiferous tubules (the developing tubuli recti) and 

 distally with the renal corpuscles (Malpighian bodies) of the meso- 

 nephric tubules (fig. 350E). The appropriated mesonephric tubules 

 form to a considerable degree the efferent ductules of the epididymis. 



(6) While the foregoing processes ensue, the sex gland gradually becomes 

 separated as a body distinct from the mesonephric kidney and appears 

 suspended from the kidney by a special peritoneal support, the 

 mesorchium. Within the mesorchium are found blood vessels, lym- 

 phatics, and the efferent ductules of epididymis (fig. 350D). 



(7) Coincident with these changes, mesenchyme between the developing 

 seminiferous tubules forms a coating of connective tissue around each 

 tubule. This connective tissue membrane gives origin to the basement 

 membrane of the seminiferous tubule. Within the tubules, epithelial 

 elements, primitive germ cells, and sustentacular elements (Chap. 3) 

 or Sertoli cells appear. The Sertoli cells extend from the connective- 

 tissue wall of the tubule inward between the epithelial and genitaloid 

 cells. The genital cells lie close to the surrounding connective-tissue 

 or basement membrane (figs. 8; 350F). 



(8) Between the developing seminiferous tubules, the various cells, blood 

 vessels, etc., of the interstitial tissue begin to appear (fig. 350F; see 

 Chap. 1). 



(9) Accompanying the foregoing transformations, the primitive tunica 

 albuginea, which originally appeared as a narrow area, containing a 

 few scattered cells between the germinal epithelium and the sex cords, 

 becomes thickened and develops into a tough, connective-tissue layer, 

 surrounding the testicular structures and separating the latter from 

 the covering coelomic epithelium. This appearance of the tunica albu- 

 ginea is one of, the characteristic features of testicular development. 

 Extending from the tunica albuginea inward between small groups of 

 seminiferous tubules as far as the rete area or mediastinum, connective- 

 tissue partitions are formed. These partitions are the septula. Each 

 septulum comes to surround a small group of seminiferous tubules 

 and thus divides the testis into compartments or lobules (fig. 7). 

 Within each lobule, several seminiferous tubules are found, with the 

 tubuli contorti or twisted portion of the tubules lying distally within 



