iQoS] YAMANOUCHI—SPOROGENESIS IN NEPHRODIUM 7 



presented in fig, 4 has been described 



bein 



However^ the shortening of the cbromosomes pr 

 until the bent ends Ivine at the equatorial region be 



and the chromo 



thus there is established 



.ge in which the chromosomes are arran 



plate (fig. 5)- The two daughter chromosomes formed by the longi- 

 tudinal splitting of a single one at prophase have remained side by 



and have been 



seem 



size and form. When this stage 

 the two daughter chromosomes 

 This stage is less frequently met 



\ m material favorablv fixed and 



g an abundance of stag 



many daughter chromosomes generally begin 



and Droceeds sim 



hich seuarate after their ass 



on the way toward the poles. The chromosomes arranged in the 

 equatorial plate are perfectly straight; the separation of the two 

 halves begins at the ends where the spindle fibers are attached and 

 proceeds toward the other end, necessarily 



catismg a curvmg, as 



fig, 6; but soon 



resume their straight form and so persist. W^en the two sets of 

 daughter chromosomes reach nearly to the pol.^. they become per- 

 fectly parallel, without overlapping {fig. 8)^ and in the more favorable 

 cases they are as regular!}' placed as if they stood in one plane, a 

 sta^e which is the most satisfactory for counting. The polar view 



or 132. 



stage ifig^ 9) shows that the number of chromosomes 

 During prophase and even metaphase the number c 

 mcBomes could sometimes be estimated, especially in the pel 

 at the equatorial plate stage, 

 early telophase - 



such cxacmess as 



le chromosomes grouped at the pole are dia^vm so tightly together 

 that the ends toward the pole become closer than the ends .directed 

 toward the equatorial region. This aggregation process goes^ on 

 farther and there results an extremely dense mass, in which it is 

 rlTff;^„Tt ir^ trj,.^^ tliP mitlinps of each chromosome. The chromosomes 



