MAMMALIAN TESTIS 



325 





Fig. 5.8. Spermiogenesis in the rat. 1 to 3, Golgi phase. The idiosome produces two 

 proacrosomic granules, which fuse into the single acrosomic granule. 4 to 7, cap phase. 

 The acrosomic granule produces the head cap, which enlarges to cover a third of the 

 nucleus. 8 to 14, acrosome phase. The nucleus and head cap elongate, whereas the acrosomic 

 granule transforms into the acrosome. 15 to 19^ maturation phase. Near the end of this 

 phase, the reactivity of the head cap and acrosome decreases considerably, and the sperma- 

 tozoon is released into the lumen (19). (From C. P. Leblond and Y. Clermont, Ann. New 

 York Acad. Sc, 55, 548, 1952.) 



ward. In stage 18, the perforatorium ap- 

 pears. In stage 19, the staining capacity 

 of the sperm is sharply reduced. 



The behavior of the remaining cells of 

 the germinal epithelium now can be corre- 

 lated. Five peaks of mitosis occur in the 

 spermatogonia. The first three peaks give 

 rise to type A spermatogonia, the fourth 

 peak to type B spermatogonia, and the fifth 

 to spermatocytes. Spermatocytes, formed 

 in stage 6, undergo the long meiotic division 

 and become spermatids at stage 1 of the 

 third cycle. 



This quantitative method has been ap- 

 plied to three areas which are of importance 



to the experimental or clinical endocrin- 

 ologist: renewal of stem cells, postnatal de- 

 generation of germ cells, and the effects of 

 hypophysectomy on the germinal epithe- 

 lium. 



The renewal of spermatogonia always has 

 been puzzling. It was postulated that they 

 were renewed from the Sertoli cells, from 

 unequal mitosis of a spermatogonium into 

 a spermatocyte and another spermatogo- 

 nium or from type A cells which did not 

 difTerentiate into type B cells. Clermont 

 and Leblond (1953) proposed a new theory 

 for the renewal of stem cells. Three types of 

 spermatogonia are present in the rat and 



