SPERMATOGENESIS OF LEPISMA DOMESTICA 395 



When the centrosome is in contact with the nuclear wall, 

 one usually sees a granule at its inner end (fig. 66), and later a 

 granule similar in size located near it on the membrane (fig. 67). 

 This suggests the breaking away or division of the granule at 

 the base of the centrosome. 



The centrosome may now change its position, being found in 

 the region of the nebenkern or even at the opposite side, and 

 shortly the delicate axial filament is seen pushing from the 

 cell and occasionally carrying a small clump of cytoplasm with 

 it, very much as has been described by Buder ( J 15) in the Lepi- 

 doptera and called by him 'plasmaklumpchen.' 



The single granule arising from the centrosome increases 

 considerably in size and divides, giving rise to two granules which 

 move apart and come to lie against the nuclear membrane and 

 closely applied to it (figs. 65, 70, 71, 72, and 73). About this 

 time or a little later a somewhat larger, round body condenses 

 out of the nebenkern ring, as shown in figure 72. 



Outside of the breaking up of the idiochromosomes and a 

 slight tendency to become pale and homogeneous, the nucleus 

 remains the same during the above changes in the cytoplasmic 

 inclusions. In the stage which follows, the delicate axial fila- 

 ment is quite obvious and its outgrowth from the distal end of 

 the rod centrosome is very clear. The rod has swung so that 

 now it is in contact with the nucleus throughout its entire length 

 and the thread is seen traversing the space between nucleus and 

 cell wall (fig. 74). The nucleus contains numerous dark-staining 

 granules. The spindle remains are prominent, their borders have 

 increased in thickness, and now appear as irregular-shaped thick- 

 walled vesicles. The nebenkern ring, cleared of the spindle 

 remains and of the various granules as well as of several aggre- 

 gations of granular mitochondria, now rounds itself up into an 

 oval-shaped dense mass which later becomes round (fig. 76). 

 No structure is at first apparent except a heavily stained granular 

 body, but one soon sees a vacuolization of its border and we 

 get the rosette nebenkern of many writers (fig. 74) . 



Of the three granules already mentioned, those arising from 

 the centrosome have either disappeared or have become so 



