278 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ZOOLOGICAL LABORATORY. 



a paired structure as Montgomery ('05) suggested. In late 

 anaphases and early prophases of the spermatogonia the other 

 chromosomes also seem each to be enclosed, more or less, in 

 separate sacs or pouches, which are, however, in communica- 

 tion with each other by means of the larger cavity of the nu- 

 cleus into which they all open. These sacculations are, how- 

 ever, not nearly so prominent as that of the accessory. These 

 observations agree with the conditions that Sutton ('00) found 

 in Brachystola magna. In the earlier cells the accessory shows 

 that it is reticular in structure, like other chromosomes, though 

 not inclined to open out so much as they. The nucleoli in these 

 cells (fig. 7) do not stain so intensely as they do afterwards. 



Figures 8 and 9 represent a somewhat later stage, possibly 

 the telophase between the last two spermatogonial divisions. 

 The reticular structure of the accessory still persists. It is 

 much like the other chromosomes, but just a little more regu- 

 lar in outline and more condensed. The membrane or sac 

 enclosing the accessory in figure 8 seems to extend into the 

 center of the nucleus, but this is only apparent. Instead it 

 lies in the upper part, extending over the inner side of the 

 upper wall. Figure 9 is a cell from the same cyst, showing a 

 cross-section of the accessory in its sac. In focusing through 

 the cell from top to bottom it can be seen without doubt that 

 this is the same structure found in the preceding cell. The other 

 chromosomes in this cell appear also in cross-section. Two 

 nucleoli seem to be present in every cell of the cyst. They are 

 somewhat larger than in figure 7 and stain more intensely. 



After the last spermatogonial division the nucleus is at its 

 smallest volume. The chromosomes, except the accessory, 

 loosen up and take on a reticular condition. The accessory 

 retains its homogeneous and more or less condensed state, 

 staining red with the tricolor (fig. 10). It becomes very ir- 

 regular in outline, thus indicating a tendency to behave like 

 the other chromosomes. The nucleoli are present and stain 

 red, though not so intensely as does the accessory. Figure 11 

 is a still later stage, where the chromatin has become very 

 much loosened. The nucleoli seem to share this same condi- 

 tion of loosening, as they are stained very pale, almost a violet, 

 but instead of becoming granular they continue to be homo- 

 geneous. 



From figure 12 on, the nuclei belong to the spermato- 



