MATURATION. 



13 



spermatocyte gives rise therefore to four spermatids in which the number of 

 chromosomes is reduced to one-half the normal. 



After the last spermatocyte division and the resulting formation of the 

 spermatid, the nucleus of the latter acquires a membrane and intranuclear 

 network, thus passing into the resting condition. Without further division 



FIG. 7. Reduction of chromosomes in spermatogenesis in Ascaris megalocephala (bivalens). 

 Brauer, Wilson. A G, Successive stages in the division of the primary spermatocyte. 

 The original reticulum undergoes a very early division of the chromatin granules which 

 then form a doubly split spireme (B). This becomes shorter (C), and then breaks in two 

 to form the 2 tetrads (D, in profile, E, on end). F, G, H, First division to form 2 secondary 

 spermatocytes, each receiving 2 dyads. /, Secondary spermatocyte. /, K, The same 

 dividing. L, Two resulting spermatids, each containing 2 single chromosomes. 



the spermatid now becomes transformed into a spermatozoon (Fig. 8). This 

 is accomplished by rearrangement and modification of its component struc- 

 tures. The centrosome either divides completely, forming two centrosomes, or 

 partially, forming a dumbbell-shaped body between the nucleus and the sur- 

 face of the cell. The nucleus passes to one end of the cell and becomes oval 



