2O J. E. WODSEDALEK. 



migrates to a point directly opposite the centrosome in contact 

 with the wall on the other side (Figs. 66, 67 and 68). The sphere 

 in this process of migration is in such close contact with the 

 nuclear wall that a slight depression can be detected in the latter. 

 The depression is even more pronounced when the clear sphere 

 becomes definitely fixed as the small acrosome (Figs. 68-75). 



In the guinea-pig the acrosome, which becomes nearly as large 

 as the nucleus itself, according to Meves ('99), is also formed 

 from the centrosphere or idiozome. While in the rat, according 

 to Lenhossek, it is independently formed in the cytoplasm 

 without relation to the preceding mitotic figure or the centro- 

 somes. Meves ('97) also found that in the salamander the 

 acrosome is formed from the idiozome which wanders around 

 the nucleus to its anterior pole. McGregor's results on Am- 

 phiuma ('99) agree in general with those of Meves, except that 

 here the acrosome arises from only a part of the centrosphere, 

 while a second smaller part passes to the base of the nucleus and 

 forms the main part of the middle-piece. Coincidentally with 

 the division of the centrosome and the migration of the small 

 sphere the nucleus together with these structures moves to one 

 side of the cell in the direction of the acrosome and soon prac- 

 tically all of the cytoplasm is at the posterior end of the cell 

 (Figs. 66, 67, 68, 69 and 70). The cell wall seems to persist as a 

 thin mantle covering the head of the spermatozoan. 



The anterior part of the cell, bearing the acrosome, almost 

 invariably points in the direction of the tubule wall while the 

 mass of cytoplasm extends into the lumen (Fig. 2). Most of the 

 chromatic material of the nucleus gathers at the center into a 

 dense mass which has the same staining capacity as characterizes 

 the chromosomes and the centrosome. Sometimes two or three 

 masses are present (Figs. 73, 74 and 75). 



Soon after the division of the centrosome into a cylindrical 

 anterior and a disc-shaped posterior body, a divergence of the 

 two follows, but they remain connected by a streak of material 

 (Fig. 69). The inner body upon coming in contact with the 

 nuclear wall forms a depression in the latter and its anterior 

 portion shapes into a disc which comes in close contact with the 

 nuclear wall in the small depression at the posterior end of the 



