THE MALE 



37 



Primary 

 spermatocyte 



Secondary 

 spermatocytes 



Sertoli cell 



Spermatogonia 



Second maturation 

 division figures 



Spermatids 



Lumen of tubule 



Heads of 



mature spermatozoa 



Spermatogenetic stages in the seminiterous tubule of the frog testis. 



tails of the clustered mature spermatozoa project into the lumen of 

 each seminiferous tubule. 



If one studies the July or August testis, which organ is then in 



its height of spermatogenetic activity, he can find all the stages of 



(Continued from opposite page.) 

 the interstitial tissue, spermatogonia, and a few primary spermatocytes. The 

 post-breeding condition. (C) High-power magnification of "A." (D) High-power 

 magnification of "B." (E) Testis of an August frog, showing all stages of 

 spermatogenesis. (F) Partially (pituitary) activated testis, similar to "E," show- 

 ing released spermatozoa within the lumen, and all stages of spermatogenesis 

 around the periphery of the seminiferous tubule. (G) Testis of a hibernating, 

 pre-breeding frog. Note the clusters of mature spermatozoa attached to single 

 Sertoli cells. The lumen is filled with tails, few spermatogonia, and primary 

 spermatocytes around the periphery of the seminiferous tubule. (H) Testis of 

 the male during amplexus, showing spermatozoa liberated into the lumen of the 

 seminiferous tubule. (I) Collecting tubule of the frog testis full of mature sper- 

 matozoa, showing their origin from the connecting seminiferous tubules. Col- 

 lecting tubules are lined with low cuboidal epithelium and are continuous with 

 the vasa efferentia and the Malpighian corpuscles of the kidney. 



