﻿512 
  J. 
  BBETLAND 
  FARMER 
  AND 
  J. 
  E. 
  S. 
  MOORE. 
  

  

  chromosomes 
  are 
  formed 
  in 
  this 
  way, 
  and 
  as 
  a 
  matter 
  of 
  fact 
  

   they 
  are 
  not. 
  Sometimes 
  two 
  more 
  or 
  less 
  straight 
  rodlets 
  

   become 
  approximated 
  with 
  or 
  without 
  interlacing, 
  whilst 
  at 
  

   others 
  the 
  ends 
  of 
  the 
  rodlets 
  may 
  unite 
  together 
  so 
  as 
  to 
  

   give 
  rise 
  to 
  figures 
  of 
  rings, 
  ellipses, 
  etc. 
  These 
  various 
  figures 
  

   (c 
  f. 
  Figs. 
  11-13) 
  may 
  originate 
  in 
  various 
  ways, 
  and 
  it 
  is 
  

   not 
  necessary 
  to 
  discuss 
  them 
  more 
  fully. 
  ^ 
  The 
  important 
  

   point 
  to 
  bear 
  in 
  mind 
  is 
  this, 
  that 
  the 
  two 
  rods, 
  sides 
  of 
  loops, 
  

   or 
  whatever 
  other 
  form 
  the 
  structure 
  as 
  a 
  whole 
  may 
  assume, 
  

   represent, 
  not 
  the 
  longitudinal 
  halves 
  of 
  a 
  split 
  thread, 
  but 
  

   the 
  approximation 
  of 
  serially 
  distinct 
  regions 
  of 
  the 
  

   spireme 
  as 
  a 
  whole. 
  Thus 
  each 
  heterotype 
  chi-omosome 
  is 
  

   a 
  bivalent 
  structure, 
  and 
  their 
  " 
  reduced 
  " 
  number 
  (i. 
  e., 
  

   half 
  that 
  of 
  the 
  somatic 
  chromosomes) 
  is 
  due 
  to 
  the 
  approxima- 
  

   tion 
  and 
  more 
  or 
  less 
  intimate, 
  though 
  temporary, 
  union 
  of 
  

   the 
  equivalents 
  of 
  pairs 
  of 
  somatic 
  chromosomes. 
  

  

  It 
  will 
  be 
  convenient 
  to 
  speak 
  of 
  the 
  compound 
  (paired) 
  

   structures 
  which 
  are 
  thus 
  formed 
  as 
  chromosomes, 
  although 
  

   it 
  must 
  be 
  remembered 
  that 
  each 
  is 
  in 
  reality 
  a 
  double 
  or 
  

   bivalent 
  body. 
  As 
  they 
  become 
  shorter 
  and 
  thicker, 
  they 
  

   become 
  more 
  homogeneous, 
  and 
  all 
  trace 
  of 
  the 
  primary 
  

   fission 
  (second 
  fission 
  of 
  other 
  authors) 
  becomes 
  completely 
  

   obliterated. 
  The 
  nucleus 
  shrinks 
  in 
  size, 
  now 
  measuring 
  

   about 
  30 
  fx 
  in 
  diameter. 
  The 
  nucleolus, 
  although 
  it 
  has 
  lost 
  

   much 
  of 
  its 
  substance, 
  is 
  still 
  recognisable 
  as 
  a 
  large, 
  often 
  

   irregularly-shaped 
  body, 
  or 
  it 
  may 
  have 
  fragmented 
  into 
  a 
  

   number 
  of 
  smaller 
  pieces. 
  A 
  very 
  characteristic 
  phase 
  then 
  

   comes 
  on. 
  The 
  chromosomes 
  act 
  as 
  though 
  affected 
  by 
  a 
  

   mutual 
  repulsion, 
  and 
  instead 
  of 
  being 
  more 
  or 
  less 
  massed 
  

   together 
  towards 
  the 
  centre 
  of 
  the 
  nucleus, 
  they 
  move 
  apart 
  

   and 
  lie 
  at 
  the 
  periphery 
  of 
  the 
  nucleus, 
  the 
  nuclear 
  wall 
  

   becomes 
  thinner, 
  and 
  nucleolar 
  matter 
  escapes 
  from 
  the 
  

   nucleus 
  into 
  the 
  cytoplasm. 
  Often, 
  indeed, 
  it 
  seems 
  as 
  if 
  it 
  

   were 
  forcibly 
  ejected. 
  

  

  The 
  characteristic 
  cytoplasmic 
  radiations 
  now 
  appear, 
  

  

  ^ 
  Cf. 
  Tarmer 
  and 
  Moore, 
  " 
  On 
  the 
  Essential 
  Similarities 
  existing 
  between 
  

   the 
  Heterotype 
  Nuclear 
  Divisions 
  in 
  Animals 
  and 
  Plants," 
  'Anat. 
  Anz.,' 
  1895. 
  

  

  