Explanation of Plate II. 



All drawings were made by the author with the aid of a camera lucida. All 

 figures except 2, 3, 4 and 45 were made with a B. & L. ,',; objective and one-inch 

 eve-piece, producing a magnification of 1340 diameters. Figs. 2, 3, 4 and 45 were 

 drawn with a Leitz ,',. objective and a Zeiss compensating ocular No. 12, giving 

 a magnification of 2325 diameters. The drawings were not reduced in the photo- 

 mechanical reproduction. 



Fig. 1. An early telophase, in which the fibers appear like barrel staves. 

 Some of the fibers have thickened. 



Fig. 2. A later stage, in which the fibers are uniting, the clear space is 

 forming, and the chromosones are beginning to separate. 



Fig. 3. A daughter-cell, showing the chromosomes separating and the fibers 

 thickening. 



Fig. 4. The chromosomes are scattered over the nuclear membrane ; the fibers 

 appear as a few thick rods. The beginning of the acrosome is seen. The acces- 

 sory chromosome can be distinguished. 



Fig. 5. Same as fig. 4, with some of the fibers curved and no acrosome. 



Fig. 6. Same as fig. 5, but with the acrosome visible. 



Fig. 7. The chromosomes are granular; the fibers have bent and formed the 

 round "striated nebenkern." The acrosome is present. 



Fig. 8a. Same as fig. 7, but the acrosome is not present. 



Fig. 8&. The fibers run parallel with the long axis of the nebenkern. 



Fig. 9. Here is shown a partial end view of the nebenkern. The accessory 

 chromosome and the acrosome are both prominent. 



Fig. 10. The nebenkern shows some of the fibers on the under side. It is be- 

 ginning to break up. 



Fig. 11. The nebenkern shows the beginning of the dark center; the fibers 

 extend from it to the ring. The acrosome has a peculiar appearance. 



Fig. 12. The fibers have broken up and the whole has assumed a vesicular 

 appearance, resembling a blackberry. The acrosome is present. 



Fig. 13. This shows a persisting spermatid stage. The chromatin appears in 

 patches. The nebenkern is in the ball-and-ring stage. The acrosome shows its 

 characteristic clear center surrounded by a ring darker on one side. The two 

 dark bodies on the nuclear surface are probably artefacts. 



Fig. 14. A stage a little later than 13. The dark central ball shows some 

 vacuoles. The cell is beginning to elongate. 



Fig. 15. Same as fig. 14, with the ball denser. 



Fig. 16. The nucleus has become almost clear. The acrosome is behind the 

 nebenkern. 



Fig. 17. This shows the axial filament apparently growing out from the 

 nucleus. There is an aggregation of chromatin at its base. 



