﻿576 
  S. 
  E. 
  S. 
  MOORB 
  ANJ) 
  L. 
  bl. 
  ROBINSON. 
  

  

  radiating 
  stfiatiou^ 
  exteiidiug 
  out 
  from 
  the 
  archoplasm 
  ov(U' 
  

   the 
  nuclear 
  contents. 
  The 
  ceutrosomes 
  rapidly 
  move 
  apart, 
  

   and 
  the 
  chromatic 
  loops 
  fall 
  asunder. 
  The 
  free 
  ends 
  of 
  each 
  

   of 
  the 
  loops 
  are 
  now 
  seen 
  to 
  have 
  fused 
  together, 
  giving 
  rise 
  

   to 
  the 
  typical 
  heterotype 
  ring 
  chromosomes 
  (tig. 
  15). 
  

  

  The 
  fragments 
  of 
  the 
  nucleolus, 
  which 
  have 
  usually 
  been 
  

   imprisoned 
  in 
  the 
  cluster 
  of 
  loops, 
  are 
  now 
  liberated, 
  and, 
  as 
  

   the 
  spindle 
  rapidly 
  develops, 
  tliey 
  pass 
  to 
  the 
  periphery 
  of 
  

   the 
  nucleus, 
  and 
  are 
  finally 
  thrown 
  out 
  into 
  the 
  cytoplasm. 
  

  

  These 
  fragments 
  persist 
  for 
  some 
  time, 
  being 
  visible 
  after 
  

   the 
  homotype 
  division 
  has 
  taken 
  place 
  as 
  a 
  number 
  of 
  small 
  

   spherical 
  masses 
  of 
  chromatic 
  substance 
  in 
  the 
  cytoplasm. 
  

   They 
  finally 
  degenerate 
  and 
  undergo 
  absorption 
  (iigs. 
  IG 
  — 
  

   18). 
  

  

  The 
  Second 
  Maiotic 
  (Homotype) 
  Division. 
  — 
  Imme- 
  

   diately 
  after 
  the 
  completion 
  of 
  the 
  heterotype 
  division, 
  the 
  

   nuclei 
  of 
  the 
  daughter 
  cells 
  do 
  not 
  enter 
  a 
  complete 
  resting 
  

   stage, 
  the 
  formation 
  of 
  the 
  chromosomes 
  proceeding 
  almost 
  

   immediately. 
  The 
  chromosomes 
  appear 
  as 
  small 
  angular 
  

   masses, 
  united 
  by 
  strands 
  of 
  linin, 
  which 
  are 
  studded 
  with 
  

   granules 
  of 
  chromatin 
  (tig. 
  19). 
  The 
  chromatin 
  present 
  in 
  

   the 
  linin 
  strands 
  gradually 
  disappears 
  as 
  the 
  chromosomes 
  

   mature, 
  being 
  used 
  up 
  in 
  this 
  maturation 
  process. 
  

  

  The 
  chromosomes 
  do 
  not 
  all 
  develop 
  at 
  the 
  same 
  rate 
  ; 
  it 
  

   is 
  usual 
  to 
  find 
  perfectly-formed 
  chromosomes 
  in 
  the 
  same 
  

   nucleus 
  in 
  company 
  with 
  the 
  rudimentary 
  angular 
  masses 
  

   (fig. 
  20). 
  The 
  homotype 
  chromosomes 
  like 
  the 
  somatic, 
  

   exhibit 
  a 
  dual 
  nature 
  almost 
  from 
  the 
  time 
  of 
  their 
  differen- 
  

   tiation, 
  and, 
  when 
  mature, 
  are 
  very 
  similar 
  in 
  appearance 
  to 
  

   those 
  of 
  the 
  somatic 
  nucleus. 
  They 
  consist 
  of 
  short, 
  curved, 
  

   thick 
  rods, 
  the 
  swollen, 
  free 
  extremities 
  of 
  which 
  give 
  rise 
  to 
  

   an 
  appearance 
  of 
  tetrads 
  arranged 
  on 
  the 
  periphery 
  of 
  the 
  

   nucleus 
  (figs. 
  20 
  — 
  22). 
  The 
  spindle 
  appears 
  at 
  this 
  tune 
  (tig. 
  

   22), 
  and 
  as 
  the 
  chromosomes 
  pass 
  on 
  to 
  the 
  spindle 
  they 
  

   shorten 
  up 
  in 
  such 
  a 
  manner 
  as 
  to 
  completely 
  lose 
  their 
  

   original 
  tetrad 
  appearance 
  (tig. 
  23). 
  They 
  now 
  appear 
  on 
  the 
  

   equator 
  of 
  the 
  spindle, 
  in 
  the 
  divided 
  condition, 
  each 
  as 
  a 
  

  

  