﻿526 
  J. 
  BKETLAND 
  FARMER. 
  AND 
  J. 
  K. 
  S. 
  MOORH. 
  

  

  The 
  spireme 
  thread 
  is 
  much 
  twisted 
  and 
  convoluted 
  within 
  

   the 
  nucleus, 
  and 
  it 
  shows 
  longitudinal 
  fission 
  through 
  con- 
  

   siderable 
  portions 
  of 
  its 
  length 
  (fig. 
  32). 
  The 
  fission 
  is, 
  how- 
  

   ever, 
  very 
  transitory, 
  and 
  it 
  becomes 
  even 
  more 
  obscured 
  later 
  

   on, 
  through 
  the 
  fusion 
  of 
  the 
  split 
  halves. 
  

  

  The 
  spirem 
  now 
  shortens 
  and 
  thickens, 
  but 
  the 
  convolu- 
  

   tions 
  are 
  still 
  numerous 
  — 
  more 
  so 
  than 
  the 
  number 
  of 
  chro- 
  

   mosomes 
  ultimately 
  to 
  be 
  produced. 
  As 
  the 
  contraction 
  

   proceeds, 
  it 
  is 
  easily 
  seen 
  that 
  in 
  many 
  places 
  the 
  loops 
  of 
  

   the 
  spirem 
  are 
  adherent 
  to 
  the 
  nuclear 
  wall, 
  and 
  the 
  latter 
  

   may 
  even 
  be 
  slightly 
  pulled 
  inwards 
  at 
  these 
  spots. 
  The 
  

   chromatic 
  thread 
  rapidly 
  becomes 
  more 
  rich 
  in 
  nuclein, 
  the 
  

   nucleolus 
  contributing 
  to 
  this 
  process 
  and 
  itself 
  losing 
  a 
  large 
  

   portion 
  of 
  its 
  stainable 
  constituent. 
  The 
  filament 
  is 
  now 
  

   seen 
  to 
  break 
  up 
  into 
  its 
  definite 
  chromosomes 
  (figs 
  33-35), 
  

   and 
  in 
  number 
  these 
  are 
  sometimes 
  easily 
  seen 
  to 
  be 
  the 
  

   number 
  characteristic 
  for 
  the 
  reduced 
  number, 
  which 
  seems 
  

   to 
  be 
  eleven 
  for 
  the 
  species 
  in 
  question. 
  Each 
  chromosome, 
  

   however, 
  is 
  clearly 
  seen, 
  on 
  following 
  its 
  subsequent 
  history, 
  

   to 
  be 
  bivalent. 
  For 
  the 
  previous 
  parallel 
  arrangement 
  of 
  the 
  

   threads 
  during 
  the 
  looping-over 
  stage 
  is 
  responsible 
  for 
  the 
  

   simulation 
  of 
  the 
  duplicate 
  character 
  to 
  be 
  observed 
  in 
  each 
  

   chromosome 
  at 
  this 
  period. 
  In 
  the 
  most 
  frequently 
  recurring 
  

   forms, 
  the 
  bivalent 
  chromosomes 
  at 
  this 
  stage 
  resemble 
  

   double 
  rods, 
  which 
  might 
  easily 
  be 
  mistaken 
  for 
  the 
  shortened 
  

   and 
  thickened 
  halves 
  resulting 
  from 
  the 
  previously 
  recorded 
  

   longitudinal 
  fission 
  did 
  not 
  the 
  intervening 
  stages 
  preclude 
  

   such 
  an 
  explanation. 
  Very 
  often 
  the 
  transverse 
  delimitation 
  

   give 
  rise 
  to 
  a 
  bent- 
  V-shaped 
  body, 
  the 
  two 
  limbs 
  of 
  which 
  

   represent 
  a 
  continuous 
  length 
  of 
  the 
  original 
  spirem, 
  and 
  

   hence 
  clearly 
  betray 
  the 
  bivalent 
  character 
  of 
  the 
  chromo- 
  

   some. 
  It 
  may 
  happen, 
  however, 
  that 
  the 
  halves 
  become 
  

   entirely 
  separated 
  from 
  each 
  other, 
  and 
  independently 
  of 
  any 
  

   bending 
  over 
  of 
  the 
  thread. 
  But 
  nevertheless 
  they 
  come 
  

   together 
  so 
  that 
  the 
  reduced 
  number 
  of 
  (bivalent) 
  chromo- 
  

   somes 
  is 
  affected. 
  In 
  cases 
  such 
  as 
  that 
  just 
  mentioned 
  the 
  

   conjugation 
  of 
  somatic 
  chromosomes 
  during 
  the 
  heterotype 
  

  

  