v^ 



r^' 



PLATE LXIX. 



Figs, 1, 2 and 3. — Polar views of the single daughter groups of chro- 

 mosomes resulting from the first spermatocyte division. This stage is of 

 very brief duration following immediately that in figure 25, plate LXVIII. 



Fig. 4. — A group of drawings of the accessory chromosome from stages 

 such as are shown in figures 1, 2 and 3. 



Figs. 5, 6, 7 and 8. — Polar views of the second spermatocyte complex. 

 Note difference in arrangement of the chromosomes compared with those 

 of first spermatocytes. 



Fig. 9. — Oblique view of a late first spermatocyte telophase. One whole 

 daughter group is shown and part of the other. 



Figs. 10, 11 and 12. — Lateral view of second spermatocyte spindle in 

 metaphase. (x) Accessory chromosome, (m) Small central chromosome. 



Fig. 13. — Lateral view of early anaphase, second spermatocyte. 



Fig. 14. — Later stage of the same, (x) Accessory chromosome. 



Fig. 15. — Same as figures 13 and 14, showing all of the chromosomes. 

 (») Accessory chromosome. 



Fig. 16. — Same as figure 14. 



Fig. 17. — Slightly later stage, showing the beginnings of the formation 

 of a dividing cell membrane. Note that the daughter groups of chro- 

 mosomes are entirely coalesced. This is typical of these later stages. 



Fig. 18. — Same as figure 14. 



Fig. 19, — Group of accessory chromosomes drawn from cells such as 

 are shown in figure 18, showing the constancy in size of the lagging ele- 

 ment (x). 



Figs. 20, 21, 22, 23, 24 and 25. — Later stages in the second spermatocyte 

 division, showing the behavior of the accessory chromosome (x) . Note 

 the dividing cell wall and persistent spindle fibers which identify beyond 

 a doubt the two cells shown in each figure as daughter cells of the same 

 first spermatocyte. 



Figs. 26 and 28. — Later stage of the same after the formation of the 

 nuclear membranes, (x) Accessory chromosome. 



Fig. 27. — Later stage of the same in which the spindle, fibers are 

 fading. 



Fig. 29. — Still later stage in which the two chromatin masses are 

 breaking up and the ordinary chromatin appears granular. («) Acces- 

 sory chromosome. 



Fig. 30. — A group of drawings, showing the typical appearance of the 

 daughter nuclei of the second spermatocyte which have received the ac- 

 cessory chromosome in the second maturation division. 



Fig. 31. — A group of drawings showing the early development of the 

 spermatid which received the accessory chromosome in the second mat- 

 uration division. 



