GERM CELLS AND THEIR FORMATION 



123 



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 8 

 food and energy during their 

 rapid and extensive metamor- 

 phosis into spermatozoa. In 

 some cases a very close relation 

 is established by the actual 

 embedding of one end of the 

 spermatid in the substance of 

 the basal cell. It should be 

 noticed that the function of the 

 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 

 the period of metamorphosis; 

 while in the ovary the corre- 

 sponding cells function during 

 the growth period; this is cor- 

 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 



