﻿THE 
  WAIOTIO 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  535 
  

  

  side, 
  and 
  not 
  attached 
  together 
  at 
  either 
  end. 
  Each 
  rod, 
  how- 
  

   ever, 
  is 
  longitudinally 
  split, 
  and 
  the 
  pair 
  together 
  constitute 
  

   a 
  diaschistic 
  (heterotype) 
  chromosome 
  of 
  a 
  characteristic 
  

   and 
  familiar 
  type. 
  

  

  Now, 
  as 
  is 
  well 
  knoAvn, 
  the 
  number 
  of 
  the 
  heterotype 
  

   diaschistic 
  chromosomes 
  is 
  always 
  half 
  that 
  in 
  the 
  preceding 
  

   divisions, 
  and 
  in 
  such 
  a 
  diaschistic 
  figure 
  as 
  the 
  above 
  we 
  

   have 
  a 
  condition 
  of 
  things 
  which 
  would 
  be 
  exactly 
  attained 
  if 
  

   two 
  ordinary 
  somatic 
  chromosomes 
  were 
  to 
  become 
  associated 
  

   together. 
  

  

  In 
  many 
  instances, 
  even 
  before 
  the 
  nuclear 
  membrane 
  has 
  

   disappeared, 
  we 
  have 
  found 
  that 
  the 
  short, 
  thick 
  loops 
  have 
  

   already 
  divided 
  transversely 
  in 
  their 
  curved 
  portion, 
  thus 
  : 
  ^^^ 
  

   and 
  through 
  the 
  existence 
  of 
  such 
  figures 
  we 
  immediately 
  

   see 
  how 
  those 
  diaschistic 
  (heterotype) 
  chromosomes 
  having 
  

   the 
  form 
  of 
  a 
  pair 
  of 
  actually, 
  or 
  potentially, 
  split 
  rods 
  

   have 
  been 
  produced. 
  In 
  the 
  case 
  of 
  the 
  more 
  usually 
  shaped 
  

   chromosomes, 
  as 
  division 
  proceeds 
  the 
  separation 
  of 
  the 
  loops 
  

   or 
  rings 
  into 
  two 
  halves 
  takes 
  place 
  while 
  the 
  elements 
  are 
  

   on 
  the 
  spindle, 
  and 
  is 
  brought 
  about 
  by 
  a 
  similar 
  transverse 
  

   breaking 
  of 
  the 
  curved 
  loop. 
  Or 
  the 
  process 
  may 
  be 
  still 
  

   further 
  modified 
  in 
  detail 
  in 
  a 
  number 
  of 
  ways 
  which 
  we 
  have 
  

   already 
  described 
  in 
  a 
  former 
  paper.^ 
  

  

  Whatever 
  the 
  exact 
  method 
  adopted 
  the 
  result 
  is 
  the 
  

   same, 
  and 
  it 
  comes 
  to 
  this: 
  that 
  the 
  pre-maiotic 
  number 
  of 
  

   chromosomes 
  tends 
  to 
  be 
  formed; 
  that 
  these 
  for 
  a 
  longer 
  or 
  

   shorter 
  time 
  remain 
  united 
  in 
  pairs, 
  so 
  that 
  there 
  are 
  only 
  

   half 
  as 
  many 
  chromatic 
  aggregates 
  in 
  the 
  cell 
  as 
  in 
  the 
  case 
  

   of 
  the 
  ordinary 
  pre-maiotic 
  divisions, 
  while 
  during 
  the 
  later 
  

   state 
  of 
  the 
  first 
  maiotic 
  or 
  heterotype 
  mitosis 
  the 
  united 
  

   chromosomes 
  simply 
  separate 
  from 
  one 
  another 
  and 
  pass 
  

   in 
  their 
  entirety 
  into 
  each 
  of 
  the 
  daughter 
  cells. 
  

  

  In 
  the 
  cockroach 
  there 
  are, 
  as 
  a 
  matter 
  of 
  fact, 
  two 
  chief 
  

  

  variations 
  of 
  the 
  manner 
  in 
  which 
  the 
  diaschistic 
  (heterotype) 
  

  

  chromosomes 
  are 
  arranged, 
  and 
  separate 
  from 
  one 
  another 
  on 
  

  

  the 
  spindle, 
  during 
  the 
  later 
  stages 
  of 
  division. 
  In 
  the 
  one 
  

  

  ' 
  Farmer 
  and 
  Moore, 
  loc. 
  cit. 
  

  

  