148 



THE DEVELOPMENT OF THE GAMETES OR SEX CELLS 



ACROS OME 

 CAP 



POS T - 



NUCLEAR 



CAP 



GOLGf 



R E MNANT 



Fig. 81 



Fig. 82 



Fig. 81. Later stages of human spermatogenesis. (Redrawn from Gatenby and Beams, 



1935.) 



Fig. 82. Stages of guinea-pig spermatogenesis. Observe dual nature of the acrosome; 

 also, middle-piece bead (kinoplasmic droplet). (A-C redrawn from Gatenby and Beams, 

 1935; D redrawn from Gatenby and Woodger, '21.) 



and the description given below should be regarded as being true of one type 

 of sperm only and should not be applied to all flagellate sperm. 



A fully differentiated spatulate sperm of the mammals possesses the fol- 

 lowing structural parts (fig. 77). 



a) Head. Around the head of the sperm there is a thin, enveloping layer 

 of cytoplasm. This cytoplasmic layer continues posteriad into the neck, middle 

 piece, and tail. Within the cytoplasm of the head is the oval-shaped nucleus. 

 Over the anterior half of the nucleus the apical body or acrosome is to be 

 found, forming, apparently, a cephalic covering and skeletal shield for the 



