GERM CELLS AND THEIR FORMATION 



123 



1 



original position and move out 

 toward the free surface of the 

 epithelium. Through their at- 

 tachment to the basal cells the 

 spermatids draw a supply of 

 food and energy during their 

 rapid and extensive metamor- 

 phosis into spermatozoa. In 

 some cases a very close relation 

 is established by the actual 7 

 embedding of one end of the 

 spermatid in the substance of 

 the basal cell. It should be 

 noticed that the function of the 6 

 follicle or basal cells of the 

 testis is to supply nutrition to 

 the germ cells, not so much 

 during their period of growth as 

 after that is completed, during 5 

 the period of metamorphosis; 

 while in the ovary the corre- 

 sponding cells function during 

 the growth period; this is cor- 4 

 related with the smaller size 

 of the spermatocyte and with 



FIG. 69. Diagrammatic outline of 

 the spermatogenesis of the rat in thirty- 

 two stages. After v. Ebner. Base- 

 ment membrane toward the left. 1-8. 

 Period of multiplication (the number 

 of cell generations is actually very large). 

 9-18. Period of growth. 19-24. Period 

 of maturation. 25-32. Period of meta- 

 morphosis. 6, basal cells or Sertoli 

 cells. 1-16. Spermatogonia. 17, 18. 

 Primary spermatocytes preparing for 

 division. 19. First spermatocyte divi- 

 sion. 20. Secondary spermatocytes. 

 21. Secondary spermatocyte division. 

 22-25. Spermatids. 26-31. Trans- 

 formation of spermatids. 32. Fully 

 formed spermatozoa. 



32 



