78 bulletin: museum of comparative zoology. 



examine only the stages following that division. Figure 80 (Plate 7) 

 shows a telophase of the first spermatocyte division as seen when 

 looljing from the equator toward the centrosome. There are eleven 

 dyads here, and since the whole number could easily be counted, the 

 accessory is not present. One of these dyads is more deeply stained 

 than the others, and, judging from its size relations, I think we may 

 identify this dyad as one from chromosome-pair A. This conclusion 

 receives still stronger support from figures 81 et seq. Figure 81 is of a 

 stage slightly later than the one in figure 80, and here we can see the 

 dyad A in addition to the accessory dyad, which is less deeply stained 

 than the others and is surrounded by a well-defined clear space, as 

 indicated by the dotted line. In figure 82 is drawn a telophase in 

 which the dyad A is shown in both the daughter cells. From these 

 figures (80-82) it is apparent that this element cannot be confused 

 with the accessory at these stages. In figures 83 and 84, however, it is 

 less easy to distinguish between them. But a long and careful study 

 has convinced me that the accessory, having early passed through a 

 stage of greatest diffusion, soon becomes condensed, while the other 

 dyads are undergoing dissolution. Dyad A, on the other hand, at 

 first remains more condensed than the others and then gradually be- 

 comes diffused like them. Figure 83 shows an early interkinesis stage 

 in which the large accessory dyad (X) is more condensed than that 

 shown in figure 81, but where dyad A is still more dense. In figure 84, 

 which is of a stage not much further advanced, the accessory is seen 

 to be the most condensed dyad (X), whereas A has gone far toward its 

 stage of diffusion corresponding to that of the other chromosomes. 

 That the accessory remains condensed throughout interkinesis is 

 further shown in figures 46 and 48 (Plate 4). Figure 48 further shows 

 that in the prophase of the second spermatocyte the A dyad condenses 

 earlier than any other dyads except that of the accessory. 



It was impossible to trace the A dyad into the metaphase of the 

 secondary spermatocyte, but in the telophase it may again be recog- 

 nized by its characteristic deeper staining and by its size relations. 

 In figure 55 (Plate 5), which is a polar view of such a telophase, three 

 deeply staining chromatic masses are shown. The larger one (X) is 

 probably the accessory, the next in size, the monad of A, and the 

 smallest, a monad of B (p. 79). Figure 85 (Plate 7) shows a somewhat 

 later telophase, in which diffusion has progressed a little beyond that 

 seen in figure 55. About the same relative staining qualities and 

 relative sizes are seen as in figure 55. The accessory appears in only 

 half of the secondary spermatocytes and spermatids, however, and 



