﻿392 
  ß- 
  T. 
  Young, 
  

  

  structure 
  at 
  all, 
  but 
  rather 
  a 
  pair 
  of 
  chromosomes 
  (a 
  view 
  for 
  which 
  

   there 
  is 
  not 
  the 
  slightest 
  warrant), 
  we 
  should 
  have 
  at 
  the 
  most 
  

   seven 
  instead 
  of 
  three 
  chromosomes. 
  In 
  Fig. 
  69 
  I 
  have 
  shown 
  an 
  

   equatorial 
  plate 
  containing 
  eight 
  chromosomes, 
  and 
  in 
  Fig. 
  70 
  one 
  

   containing 
  ten, 
  one 
  of 
  which 
  is 
  not 
  in 
  clear 
  focus. 
  I 
  have 
  also 
  seen 
  

   an 
  equatorial 
  plate 
  containing 
  six 
  with 
  one 
  possible 
  extra 
  chromo- 
  

   some, 
  and 
  several 
  other 
  cases 
  in 
  which 
  the 
  chromosome 
  number, 
  

   while 
  uncertain, 
  was 
  at 
  least 
  less 
  than 
  eight. 
  

  

  Following 
  the 
  formation 
  of 
  the 
  equatorial 
  plate 
  the 
  chromosomes 
  

   in 
  some 
  cases 
  separate 
  and 
  move 
  a 
  short 
  distance 
  along 
  the 
  spindle, 
  

   (Figs. 
  66 
  and 
  67). 
  There 
  is 
  no 
  evidence 
  of 
  any 
  regularity 
  in 
  the 
  

   division 
  of 
  the 
  chromosomes. 
  In 
  addition 
  to 
  irregularities 
  in 
  the 
  

   chromosomes 
  themselves 
  their 
  movement 
  along 
  the 
  spindle 
  is 
  not 
  in 
  

   any 
  regular 
  order, 
  some 
  preceding 
  the 
  others 
  and 
  forming 
  thus 
  a 
  

   straggling 
  line 
  at 
  either 
  end 
  of 
  the 
  spindle.^) 
  Their 
  position 
  relative 
  

   to 
  the 
  spindle 
  axis 
  is 
  also 
  irregular, 
  tho 
  in 
  general 
  they 
  are 
  placed 
  

   parallel 
  to 
  the 
  latter. 
  This 
  irregularity 
  in 
  chromosome 
  arrangement 
  

   has 
  been 
  noted 
  by 
  both 
  Child 
  (1907, 
  II 
  and 
  III) 
  and 
  Richards 
  (1911) 
  

   in 
  Moniesia. 
  

  

  The 
  next 
  step 
  is 
  the 
  degeneration 
  of 
  the 
  spindle 
  and 
  either 
  the 
  

   passage 
  of 
  the 
  nucleus 
  into 
  the 
  resting 
  condition 
  without 
  under- 
  

   going 
  any 
  distinct 
  anaphase 
  or 
  telophase^), 
  or 
  the 
  direct 
  

   development 
  of 
  cleavage 
  nuclei 
  from 
  the 
  chromosomes 
  as 
  will 
  be 
  

   described 
  later. 
  Eggs 
  showing 
  clearly 
  spindle 
  degeneration 
  are 
  hard 
  

   to 
  find, 
  but 
  the 
  absence 
  of 
  clear 
  anaphases 
  and 
  telophases 
  renders 
  

   it 
  probable 
  that 
  this 
  usually 
  if 
  not 
  always 
  occurs. 
  An 
  ^^^ 
  showing 
  

   this 
  condition 
  is 
  represented 
  in 
  Fig. 
  63. 
  The 
  chromosomes 
  are 
  still 
  

   present 
  as 
  an 
  equatorial 
  plate 
  lying 
  in 
  the 
  remnant 
  of 
  a 
  spindle. 
  

   Polar 
  bodies 
  are 
  absent. 
  The 
  question 
  may 
  be 
  asked, 
  what 
  is 
  there 
  

   to 
  show 
  that 
  the 
  spindle 
  here 
  is 
  degenerating 
  instead 
  of 
  forming? 
  

   A 
  comparison 
  with 
  Fig. 
  59 
  will 
  I 
  think 
  answer 
  the 
  question 
  ; 
  for 
  in 
  

   the 
  latter, 
  which 
  represents 
  spindle 
  foi-mation, 
  aster 
  development 
  

   precedes 
  that 
  of 
  the 
  chromosomes, 
  while 
  in 
  the 
  former 
  asters 
  and 
  

   spindle 
  have 
  nearly 
  vanished, 
  but 
  chromosomes 
  are 
  still 
  present. 
  

  

  1) 
  This 
  statement 
  may 
  be 
  construed 
  as 
  casting 
  doubt 
  upon 
  my 
  inter- 
  

   pretation 
  of 
  Fig. 
  67 
  above. 
  Were 
  there 
  any 
  evidence 
  that 
  the 
  mid- 
  body 
  

   is 
  composed 
  of 
  chromosomes 
  I 
  should 
  admit 
  the 
  force 
  of 
  this 
  objection. 
  

   As 
  it 
  is 
  I 
  cannot 
  do 
  so. 
  

  

  2) 
  I 
  have 
  seen 
  a 
  single 
  case 
  of 
  a 
  late 
  anaphase. 
  

  

  