SPERMATOGENESIS OF LEPISMA DOMESTICA 393 



Later (figs. 20 and 26) the rods lengthen and show small granules 

 at then- ends. At first the two rods form an angle of 180°, but 

 this angle is later decreased to 90° or less. Each rod now divides, 

 but the halves remain attached by their granule ends, forming 

 a pair of V-shaped centrosomes, each V representing a divided 

 centrosome. This whole process is a rapid one, for all stages as 

 well as the separation of the V's for some distance may be seen 

 in cells which show little change otherwise. The migration is 

 about completed and the V's nearly at the poles by the time the 

 prophase condition is reached (fig. 30). During the succeeding 

 division the apex of the V is directed toward the chromosomes, 

 while its limbs touch the surface of the cell. The V may open 

 considerably, nearly to a straight angle, so that a large part 

 of the outer surface of the rods is in contact with the cell wall. 

 The cells may also show a slight depression at the poles (fig. 39). 



The spindle fibers all lead to the centrosome region, but an 

 actual attachment of the fibers to the centrosomes, while taken 

 for granted, does not show clearly in sections. 



This V arrangement can be identified up to a late telophase of 

 the primary spermatocyte, but I have not traced it through the 

 resting stage of the second spermatocyte. Each second sperma- 

 tocyte would receive one V, but when the rods reappear in the 

 division figure they are divided, a single rod at either pole lying 

 against the inner surface of the cell wall and oriented parallel 

 to each other, but at a slight angle with the cell axis. The 

 division or separation of the V's as well as their migration to 

 opposite poles must take place during the resting period. 



The centrosome rod can be traced through every succeeding 

 stage to the early spermatid, where it may be seen lying free 

 in the cytoplasm (fig. 65). In exceptional cases, as in figure 54, 

 the rods have granules at their ends, or we may find a number of 

 granules or fragments and no rod, as in figure 58. 



The spermatid 



The young spermatid cell is considerably smaller than the 

 resting stage of the second spermatocyte. The chromosomes 

 clump together, form a nuclear membrane, and quickly break 



