376 



THE MALE REPRODUCTIVE OBGAKS 



The four types of epithelial cells 

 enumerated ahove may also be con- 

 sidered as typifying the four prin- 

 cipal stages in the origin and develop- 

 ment of the spermatozoa. Spermato- 

 genesis begins with the spermatogonia 

 which, by reproduction, differen- 

 tiation, and development, pass suc- 

 cessively through the spermatocyte, 

 spermatid, and spermatoblast stages 

 to finally produce the mature sper- 

 matozoa. In the course of this de- 

 velopment great changes are pro- 

 duced in the character of the lining 

 ^ epithelium, each of the several cell 

 types presenting many intermediate 

 phases (Fig. 305). Hence, in a given 

 lobule of the testis, tubules may be 

 found which present over and over 

 again all of the successive phases 

 of spermatogenesis, and scarcely any 

 two neighboring tubules, nor the suc- 

 cessive portions of a given tubule, 

 will at the same time present the 

 same phases of spermatogenesis. It 

 is estimated that in every 32 mm. of 

 the length of a tortuous tubule the 

 several phases of spermatogenesis are 

 repeated (von Ebner*). 



The spermatogonia are small cu- 

 boid or spheroidal cells which rest 

 upon the membrana propria. They 

 have an ovoid nucleus, rich in chro- 

 matin, and a small amount of cyto- 



FIG. 305. DIAGRAM OF THE SUCCESSIVE STAGES OF SPER- 



MATOGENESIS IN THE RAT. 



A-H, the grouping of associated stages ; O-S, the suc- 

 cessive steps, in numerical order, from the spermatogonia to 

 the discharge of the spermatosomes. (After Kolliker.) 



* Kolliker's Handbuch, III, 428. 



