PLATE LXVIII. 



Figs. 1 to 10, inclusive. — The chromosome complex of the first sperma- 

 tocyte in metaphase. (x) Accessory chi"omosome. 



Fig. 5. — An unusual condition of the first spermatocyte metaphase, 

 showing twelve elements, a-a. — Probably the disjoined halves of one of 

 the larger chromosomes which normally occurs in the ring. 



Fig. 11. — -Drawings of the accessory chromosome from cells of the 

 cyst from which fig. 6 was made, showing the constancy in size in this 

 element within a single cyst. 



Fig. 12. — Drawings of the accessory chi-omosome from cells of the 

 cyst from which fig. 7 was made. 



Fig. 13. — Drawings of the accessory chromosome from cells of the 

 cyst from which fig. 8 was made. 



Fig. 14. — Drawings of the accessoiy chromosome from cells of the 

 cyst from which fig. 9 was made. 



Fig. 15. — Drawings of the accessory chromosome from cells of the 

 cyst from which fig. 10 was made. 



Fig. 16. — Lateral view of first spermatocyte in beginning anaphase, 

 (x) Accessory chromosome. The cell membrane is shown. 



Fig. 17. — First spermatocyte spindle, in longitudinal section through 

 the accessory chromosome {x) . (a) and {b) Chromosomes of the ring 

 at equal distances from (?h), the central small chromosome. The acces- 

 sory chromosome lies outside of the ring, causing the asymmetry of the 

 spindle, as drawn. 



Fig. 18. — Same view of a slightly later stage, showing the typical 

 irregularity in the movements of the accessory chromosome {x) and the 

 central small chromosome {m) with respect to those of the ring (a) 

 and {b) . 



Fig. 19. — Later anaphase, showing the difference in organization be- 

 tween the accessory chromosome (.r) and the ordinary chromosomes. 



Figs. 20, 21 and 22. — Later successive stages of the first spermatocyte 

 anaphase, (x) Accessory chromosome. 



Figs. 23, 25 and 26. — First spermatocyte telophases, in which the acces- 

 sory chromosome (x) may still plainly be identified. 



Fig. 24. — Telophase of first spermatocyte. (x) Unusual element, 

 which is probably an undivided accessory chromosome or a persistent 

 plasmasome. 



