THE SrERlEATÜtJENESTH OF DOMESTIC MAMMALS. 229 



AVitliiii the " Scbwanzruauecliette " tlie ceutrosomcs, the axial filament and 

 tlie " chromatoidor Neljeukkörper " arc ouclosed, tbo latter having attained 

 the greatest size at the lieginuing af this stage (Figs. 72-74). 



The mitochondrial grannies :— The mitochouch-ial granules are scattered 

 throughout the cell body and agii".n increase in number (Figs. 72-74). 



Period m. 



The nucleus : — Tlie nucleus continues to elongate until its anterior part 

 begins to bend towards one side -which is destined to become a ventral part 

 of the spermatozoa (Fig. 75). At this stage all the chromatin masses entirely 

 disappear, and the nucleus thu^ becomes Inniogeueous, but takes a deep 

 methj-l-green stain with Auerbach's method (Fig. 75) From this fact it 

 seems more probable that the chromatin masses break into very small particles 

 and are distributed thi'oughout the nucleus, the main portion of these particles 

 being condensed at the nuclear wall. At the pjst-venti-al side of the nuclear 

 wall a large depression appears where the centrosome is situated (Figs. 75-77). 



Tlie centrosomes : — The posterior centrosome begins to divide into two, 

 while the anterior one comes to be placed in close contact to the nuclear 

 wall (Figs. 75, 7G). Of these two centrosomes thus formed by division of 

 the posterior one, the smaller one is placed nearer the nucleus, while the other 

 is placed outside it. The smaller one retains its spherical shape, and has the 

 axial filament attached to it. The larger centrosome now assumes a ring 

 shape and gradually increases in size, while the axial filament comes to pass 

 through the ring (Fig. 75, 77). Soon after the ring-shaped centrosome begins 

 to move backward along the axial filament (Fig. 78). 



The mitochondrial granules : — The mitochondrial granules are now gathered 

 into several groups within the elongated cell body, and these soon begin to 

 an-ango themselves around the axial filament (Figs. 77, 78). Besides the 

 mitochondria other largo gi-anules can I» seen, stained deeply with osmic 

 acid (Fig. 83). These may be fiit-granules which probably correspond to those 

 of the rat, as described by Dcesbeeg ('08 b). 



The acro.some : — The acrosome assumes a pear-shape and attaches at the 

 apex of the head of tlie spermatozoa, while the rest of the Idiozome completely 

 disappears (Figs. 75-78). 



