150 THE DEVELOPMENT OF THE GAMETES OR SEX CELLS 



Spermatid into a most complicated structure. Some of these changes are out- 

 lined below. 



a) GoLGi Substance and Acroblast; Formation of the Acrosome. 

 The Golgi substance or parts thereof previously associated with the idiosome 

 of the spermatocyte (fig. 80A) proceeds to form the acrosome of the devel- 

 oping spermatid as follows: In the differentiating human sperm, the Golgi 

 substance of the spermatocyte (fig. SOD) becomes aggregated at the future 

 anterior end of the nucleus, as shown in fig. 80F, where it forms an acroblast 

 within a capsule of Golgi substance. This acroblast later forms a large vacuole 

 within which is the acrosomal "bead" (figs. 68B; BOG). The acrosomal bead 

 proceeds to form the acrosomal cap, shown in figure 81 A, and the latter 

 grows downward over the anterior pole of the nucleus (fig. 81 A, B). Most of 

 the Golgi substance in the meantime is discarded (fig. 81 A, B). (See Gatenby 

 and Beams, '35.) 



In the guinea pig the acroblast together with other Golgi substance, mi- 

 grates around the nucleus toward the future anterior pole of the latter where 

 the acroblast takes up its new position (fig. SOB, C, E). (See Gatenby and 

 Woodger, '21.) As shown in figure 80E, the acroblast is composed of inner 

 and outer acrosomal substances. These inner and outer areas of the acroblast 

 give origin respectively to the inner and outer zones of the acrosome (fig. 82). 

 The peripheral or surrounding Golgi material of the acroblast detaches itself 

 meanwhile from the developing acrosome (fig. SOE, H) and drifts downward 

 toward the posterior end of the sperm. Eventually it is discarded with the excess 

 cytoplasm and some mitochondrial material. In some animal species (e.g., 

 grasshopper) the acrosomal substance arises from a multiple type of acroblast 

 (Bowen, '22). (See fig. 83.) Nevertheless, the general process of acrosome 

 formation is similar to that outlined above. 



b) Formation of the Post-nuclear Cap. All spatulate sperm of mam- 



NEBENK ERN 

 ( MITOC HONORI A) 



Fig. 83. Formation of the acrosome from a multiple acroblast in the grasshopper. (After 



Bowen, Anat. Rec, 24.) 



