459 



lb, pole view), but before the daughter nuclei have separated, 7 chromo- 

 somes are seen in each daughter cell, and each of these chromosomes 

 is transversely constricted. That this is a transverse and not a longi- 

 tudinal constriction is proved by the numerous cases where the con- 

 striction is already well marked on the daughter chromosome, before 

 it has left the spindle of the first spermatocyte (fig. 0); and also by the 

 fact that the constriction is perpendicular to the long axis of the 

 chromosome (figs. 7a, h). 



Fig. 5c. 



Fig. 5Ä. 



Fig. la. 



Fig. 6. 



Fig. 76. 



Fig. 8. 



Fig. 9. 



Without any intervening resting stage, the cell then passes into 

 the 2nd and last spermatocytic division. In the monaster of the latter 

 (fig. 8) the 7 chromosomes become transversely split, the line of their 

 transverse constrictions coinciding 

 with the equatorial plane of the 

 spindle. Finally, in the succeeding 

 dyaster (fig. 9), the 7 daughter chro- 

 mosomes of each daughter cell (sper- 

 matid) fuse together and form a flat- 

 tened disc of chromatin. 



In figs, ha, b, and 6 all the chromosomes are not reproduced. 



It is interesting to note that the true nucleolus divides into two, 

 about the time of, or a little before, the chromosomes become arranged 

 in the equator of the 1st spermatocyte spindle [n in figs. 5c and bd, the 

 latter presenting a stage where the chromosomes have not yet become 

 arranged in the equator). Fig. ha shows the nucleolus already divided, 

 before the chromosomes have done so; and in fig. la we find, outside 

 of the spindle fibres, half of the original nucleolus in each daughter 

 cell. Very frequently the nucleolus is seen on pole views of the chro- 

 mosome monaster of the 1st spermatocyte [n fig. 5ô), and in such cases 



33* 



