﻿THE 
  MAIOTIO 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  531 
  

  

  perfect 
  accord 
  with 
  what 
  has 
  hitherto 
  been 
  described^ 
  the 
  

   centrosomes 
  separate 
  to 
  the 
  opposite 
  ends 
  of 
  the 
  cell^ 
  where 
  

   they 
  lie 
  a 
  short 
  distance 
  within 
  the 
  bounding 
  membrane, 
  

   while 
  at 
  the 
  same 
  time 
  the 
  chi'omosomes, 
  after 
  being 
  bunched 
  

   in 
  a 
  confused 
  mass, 
  are 
  gradually 
  drawn 
  into 
  the 
  usual 
  equa- 
  

   torial 
  figui'e 
  (see 
  fig. 
  51). 
  Daring 
  this 
  process, 
  however, 
  the 
  

   short 
  split 
  rods 
  generally 
  become 
  more 
  curved, 
  and 
  since 
  they 
  

   are 
  all 
  attached 
  by 
  the 
  middle 
  of 
  this 
  curvature 
  to 
  the 
  spindle 
  

   fibres, 
  they 
  often 
  present 
  the 
  appearance 
  of 
  sharply 
  defined 
  

   tetrads, 
  the 
  inauner 
  in 
  which 
  this 
  appearance 
  is 
  produced 
  

   in 
  the 
  type 
  under 
  consideration 
  being, 
  however, 
  at 
  once 
  

   apparent 
  upon 
  comparison 
  (figs. 
  47-51). 
  It 
  must 
  be 
  admitted 
  

   that 
  these 
  tetrad 
  figures 
  occurring 
  in 
  the 
  pre- 
  maiotic 
  divisions 
  

   of 
  the 
  cockroach 
  are 
  singularly 
  like 
  those 
  described 
  among 
  

   various 
  arthropods 
  by 
  Hacker 
  and 
  others, 
  but 
  always 
  

   referred 
  by 
  these 
  authors 
  to 
  the 
  process 
  of 
  reduction, 
  and 
  not 
  

   to 
  the 
  pre-maiotic 
  stage 
  at 
  all. 
  

  

  In 
  the 
  later 
  stages 
  of 
  the 
  pre-maiotic 
  divisions 
  the 
  halves 
  of 
  

   each 
  of 
  the 
  thirty-two 
  chromosomes 
  gradually 
  separate 
  and 
  

   pass 
  away 
  to 
  the 
  poles 
  of 
  the 
  spindle 
  figure, 
  to 
  form 
  the 
  group 
  

   of 
  chromosomes 
  belonging' 
  to 
  each 
  daughter 
  nucleus, 
  and 
  the 
  

   division 
  of 
  the 
  cells 
  becomes 
  complete. 
  

  

  In 
  the 
  cockroach, 
  as 
  in 
  so 
  many 
  other 
  animals, 
  the 
  remains 
  

   of 
  the 
  spindle 
  persists 
  for 
  some 
  time 
  as 
  a 
  sort 
  of 
  band 
  connect- 
  

   ing 
  the 
  daughter 
  cells 
  together, 
  and 
  this 
  connecting 
  spindle 
  

   relic 
  may 
  still 
  be 
  encountered 
  during 
  several 
  subsequent 
  

   divisions 
  of 
  the 
  daughter 
  elements; 
  but 
  there 
  are 
  no 
  inter- 
  

   mediate 
  bodies 
  produced 
  quite 
  comparable 
  to 
  those 
  origin- 
  

   ally 
  described 
  by 
  Flemming 
  in 
  amphibia, 
  and 
  seen 
  

   subsequently 
  in 
  so 
  many 
  other 
  animal 
  forms. 
  

  

  During 
  pre-maiotic 
  divisions, 
  the 
  conspicuous 
  nucleolus 
  of 
  

   the 
  cells 
  breaks 
  up 
  and 
  is 
  formed 
  anew 
  within 
  the 
  daughter 
  

   nuclei, 
  the 
  remains 
  of 
  the 
  old 
  nucleoli 
  passing 
  into 
  the 
  cyto- 
  

   plasm 
  where 
  they 
  disappear. 
  

  

  The 
  divisions 
  of 
  the 
  pre-maiotic 
  elements 
  of 
  the 
  cockroach 
  

   can 
  be 
  followed 
  with 
  the 
  greatest 
  exactitude 
  and 
  ease 
  in 
  the 
  

   mature 
  testis 
  of 
  this 
  animal, 
  and 
  for 
  all 
  major 
  details 
  the 
  

  

  