PLATE LXXI. 



Fig. 1. — Lateral view of two second spermatocytes in early anaphase. 

 It is apparent in both of these that the accessory chromosome is already 

 in movement to one of the poles, in the upper cell to the right and in the 

 lower to the left. The accessory in the upper cell already has its longer 

 axis parallel to that of the spindle. Smear by Wilson. 



Fig. 2. — Lateral view of first spermatocyte in metaphase or early ana- 

 phase. The accessory is the lowermost chromosome. All the elements are 

 clearly seen to be divided. This is a slightly earlier stage than the ones 

 of the second spermatocytes in figure 1 and should be compared with 

 them in order to see the diflFerence in the behavior of the accessory in 

 the two divisions. Smear by Lefevre. 



Fig. 3. — Mid-anaphase of the first spermatocyte, showing the full com- 

 plex of chromosomes in each daughter cell. The accessory is the lower- 

 most one in each group and is slightly removed from the others. Smear 

 by Wilson. 



Fig. 4. — Late anaphase of the first spermatocyte mitosis. The acces- 

 sory lies to the right of each daughter group at the same level. Smear 

 by Lefevre. 



Fig. 5. — Mid-anaphase of the first spermatocyte, oblique view. The 

 accessory to the right of each daughter group. 



Fig. 6. — Mid-anaphase of the first spermatocyte anaphase,, lateral view. 

 The accessory at the lower end of each daughter group. 



Fig. 7. — Very late anaphase of the first . spermatocyte division, lateral 

 view, with the accessory chromosome of each group proximal to the 

 equatorial plate. Smear by Wilson. 



Fig. 8. — Late anaphase of the first spermatocyte mitosis, showing the 

 divided accessory accompanying each daughter group of chromosomes. 

 Smear by Lefevre. 



Fig. 9. — Like figure 8. Smear by Lefevre. 



Fig. 10. Similar to figures 8 and 9. Smear by Lefevre. This series 

 of anaphases of the first spermatocyte indicate, I think, that the accessory 

 is characterized by an independence of movement and position in the 

 group of chromosomes rather than by a "lagging" tendency. It does 

 not in any case, apparently, anticipate the poleward movement of the 

 other chromosomes, but takes part in the general division. On account 

 of its peripheral position and slighter relation to the plate of chromosomes 

 it is crowded back and therefore lies below the daughter mass of chro- 

 matin. Its position in the metaphase of the second spermatocyte depends 

 upon the degree to which it is crowded aside in the telophase of the first. 

 If it maintains its peripheral position at the level of the other chromo- 

 somes it is then an eccentric element in the metaphase of the second . 

 supeimatocyte. If, however, it lies beneath the other chromosomes in 

 the telophase it may become included within the ring of chromosomes in 

 the next metaphase. 



Fig. 11. — Polar view of second spermatocyte metaphase. In the lower 

 cell three chromosomes are shown in lateral view. The difference in the 

 arrangement of the chromosomes, as compared with the first spermatocyte, 

 is striking and apparent. Section by Wilson. 



