248 Universitij of California PuUicatious in Zoology [Vol. 16 



formed, the plate is ver,y regular in the arrangement of the equidistant 

 chromosomes, which are in some cases all in one plane. 



There is no evidence of a longitudinal splitting of the chromosomes 

 in the metaphase, but each is constricted at its middle into two equal 

 parts. The polar caps may (pi. 20, fig. 48) or may not (pi. 18, fig. 11) 

 be visible at the poles of the spindle beyond the polar masses. 



(c) Anaphask 



Eight daughter chromosomes are then drawn to each pole (pi. 18, 

 figs. 11, 13). The polar caps are evident in the fir.st stages (pi. 18, 

 figs. 6, 10), but are covered by the chromatin in the later ones (pi. 18, 

 figs. 8, 13. 14). 



The shape of the nuclear membrane conforms to that of the karyo- 

 some until the spindle fibers appear, and then to that of the general 

 shape of the whole mitotic figure. It becomes constricted in the equa- 

 torial region in the early anaphase (pi. 18, fig. 10) and the two parts 

 become more and more separated (pi. 18, figs. 13, 14). The membrane 

 finally closes around the daughter nuclei in the later anaphase (pi. 18, 

 fig. 8). 



(d) Telophase 



The polar masses become elongated at right angles to the long axis 

 of the spindle, the chromosomes are fused, and the masses become more 

 closely connected with the polar clumps ; then the peripheral chromatin 

 is extruded in each nucleus from the region between the two masses, 

 and migrates towards the nuclear membrane. There is a connection 

 between the two daughter nuclei which stains like plastin (pi. 18, 

 fig. 15) and which persists until immediately before cytoplasmic 

 division is complete (pi. 18, fig. 12). 



(f ) Nuclear Reorganization 

 In the reorganization of the nucleus, the nuclear "membrane" 

 becomes spherical, the peripheral chromatin and plastin come out from 

 the region between the polar and chromosome masses (pi. 20, figs. 50. 

 53, 57) and take their position at the nuclear "membrane." The polar 

 and chromosome masses fuse, forming a karyosome with a lighter-stain- 

 ing mass in the center (pi. 20, figs. 43, 61) which is the remains of the 

 plastin of the spindle. Most of this process takes place after the 

 daughter amoebas are separated. 



