﻿438 
  J. 
  W. 
  JENKINSON. 
  

  

  With 
  the 
  completion 
  of 
  this 
  process 
  and 
  the 
  total 
  disap- 
  

   pearance 
  of 
  the 
  nuclear 
  membranes^ 
  which 
  seem 
  to 
  be 
  used 
  

   in 
  the 
  formation 
  of 
  the 
  fibres^, 
  the 
  spindle 
  may 
  be 
  said 
  to 
  be 
  

   fully 
  established. 
  It 
  consists 
  now 
  of 
  undulating 
  fibres 
  passing 
  

   continuously 
  from 
  one 
  pole 
  to 
  the 
  other, 
  and 
  frequently 
  

   united 
  by 
  anastomoses 
  (fig. 
  39). 
  Transverse 
  sections 
  show 
  a 
  

   polygonal 
  meshwork 
  thickened 
  at 
  the 
  nodes; 
  we 
  have 
  as 
  good 
  

   reason 
  here 
  as 
  in 
  other 
  cases 
  for 
  regarding 
  the 
  fibres 
  as 
  the 
  

   optical 
  sections 
  of 
  inter-alveolar 
  lamella?. 
  The 
  spindle 
  

   increases 
  in 
  diameter 
  as 
  well 
  as 
  in 
  length. 
  

  

  Very 
  considerable 
  changes 
  have 
  been 
  meanwhile 
  taking- 
  

   place 
  in 
  the 
  pronuclei 
  also. 
  

  

  In 
  the 
  early 
  fertilization 
  spindle 
  they 
  are 
  round, 
  somewhat 
  

   irregular 
  bodies, 
  much 
  increased 
  in 
  volume 
  since 
  their 
  first 
  

   formation. 
  They 
  possess 
  a 
  fine 
  achromatic 
  reticulum, 
  chro- 
  

   matin 
  in 
  a 
  state 
  of 
  minute 
  subdivision, 
  and 
  true 
  nucleoli 
  or 
  

   plasmosomes 
  (figs. 
  31, 
  32). 
  In 
  this 
  condition 
  they 
  remain 
  

   during 
  the 
  early 
  stages, 
  except 
  that 
  they 
  become 
  enlarged 
  

   and 
  lengthened 
  in 
  the 
  direction 
  of 
  the 
  spindle 
  axis 
  (fig. 
  32), 
  

   but 
  when 
  the 
  latter 
  is 
  beginning 
  to 
  elongate 
  the 
  chromatin 
  

   granules 
  increase 
  both 
  in 
  size 
  and 
  number 
  (fig. 
  33). 
  The 
  

   total 
  quantity 
  of 
  chromatin 
  in 
  the 
  nucleus 
  seems 
  therefore 
  to 
  

   be 
  greater 
  than 
  before, 
  as 
  though 
  it 
  had 
  been 
  reprecipitated 
  

   from 
  solution. 
  

  

  Of 
  the 
  first 
  steps 
  in 
  the 
  production 
  of 
  the 
  chromosomes 
  I 
  

   can 
  say 
  very 
  little 
  (fig. 
  36). 
  In 
  the 
  earliest 
  stage 
  which 
  I 
  

   have 
  irregular 
  moniliform 
  chromatic 
  threads 
  are 
  scattered 
  

   through 
  the 
  nucleus; 
  their 
  length 
  is 
  variable, 
  and 
  they 
  

   appear 
  to 
  be 
  in 
  process 
  of 
  formation 
  by 
  the 
  linear 
  aggrega- 
  

   tion 
  of 
  granules. 
  In 
  this 
  stage 
  the 
  nucleoli 
  are 
  still 
  to 
  be 
  

   seen, 
  but 
  later 
  they 
  disappear. 
  The 
  chromosomes 
  certainly 
  

   do 
  not 
  arise 
  directly 
  from 
  them. 
  

  

  The 
  chromosomes 
  appear 
  separately 
  in 
  each 
  pronucleus, 
  

   while 
  the 
  nuclear 
  membranes 
  are 
  still 
  intact 
  (figs. 
  34, 
  38), 
  

   Each 
  chromosome 
  is 
  a 
  twisted 
  rod 
  of 
  uniform 
  thickness, 
  

   showing 
  very 
  little, 
  if 
  any, 
  traces 
  of 
  the 
  earlier 
  moniliform 
  

   structure. 
  The 
  chromosomes 
  lie 
  scattered 
  throughout 
  the 
  

  

  