﻿THE 
  MAIOTIC 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  539 
  

  

  which 
  at 
  first 
  emerges 
  from 
  the 
  resting 
  nucleus 
  gradually 
  

   becomes, 
  as 
  in 
  the 
  cockroach, 
  more 
  and 
  more 
  polarised; 
  and, 
  

   just 
  as 
  in 
  the 
  insect, 
  we 
  have 
  found 
  that 
  the 
  subsequent 
  

   metamorphosis 
  consists 
  of 
  a 
  gradual 
  thickening 
  of 
  the 
  in- 
  

   dividual 
  threads 
  and 
  an 
  unfolding 
  of 
  the 
  contraction 
  figure 
  

   into 
  a 
  coarse 
  spirem 
  which 
  in 
  its 
  fully-developed 
  condition 
  is 
  

   evenly 
  distributed 
  over 
  the 
  surface 
  of 
  the 
  nucleus. 
  At 
  about 
  

   this 
  period 
  many 
  of 
  the 
  individual 
  threads 
  can 
  be 
  seen 
  to 
  be 
  

   longitudinally 
  split, 
  and 
  the 
  cells 
  then 
  remain 
  for 
  a 
  long 
  

   period 
  in 
  the 
  same 
  condition, 
  the 
  threadwork 
  merely 
  becom- 
  

   ing 
  thicker 
  and 
  more 
  chromatic 
  as 
  time 
  goes 
  on. 
  When 
  

   this 
  period 
  has 
  come 
  to 
  an 
  end, 
  as 
  in 
  the 
  cockroach, 
  the 
  

   thi'eads 
  become 
  once 
  more 
  polarised, 
  and 
  this 
  contraction 
  

   corresponds 
  with 
  the 
  second 
  synaptic 
  figure 
  previously 
  de- 
  

   scribed. 
  We 
  have 
  found, 
  moreover, 
  that 
  in 
  the 
  elasmol 
  -ranch 
  

   as 
  in 
  the 
  cockroach, 
  these 
  secondary 
  loops 
  are 
  unquestionably 
  

   to 
  be 
  regarded 
  as 
  the 
  individual 
  forerunners 
  of 
  the 
  dias- 
  

   chistic 
  (heterotype) 
  chromosomes; 
  their 
  sides 
  present 
  an 
  

   obvious 
  longitudinal 
  split, 
  and 
  in 
  many 
  cases 
  the 
  loops 
  be- 
  

   come 
  twisted 
  upon 
  themselves 
  as 
  they 
  do 
  in 
  plants; 
  in 
  fact, 
  

   all 
  the 
  various 
  types 
  of 
  diaschistic 
  (heterotype) 
  chromosomes 
  

   are 
  found 
  to 
  which 
  we 
  have 
  already 
  referred. 
  

  

  Now, 
  in 
  the 
  amphibia 
  which 
  had 
  been 
  described 
  before 
  We 
  

   had 
  examined 
  the 
  elasmobranchs 
  spermatogenesis 
  the 
  hollow 
  

   of 
  the 
  heterotype 
  loop. 
  The 
  aperture 
  in 
  the 
  ring, 
  or 
  the 
  space 
  

   between 
  the 
  twisted 
  rods 
  with 
  open 
  ends, 
  had 
  always 
  been 
  

   regarded 
  by 
  Flemming, 
  Meves, 
  and 
  others 
  as 
  the 
  opened-out 
  

   portions 
  of 
  the 
  original 
  longitudinal 
  split 
  traversing 
  the 
  

   spirem 
  thread 
  ; 
  but 
  when 
  that 
  which 
  happens 
  in 
  the 
  cock- 
  

   roach 
  is 
  borne 
  in 
  mind, 
  it 
  becomes 
  obvious 
  that 
  all 
  the 
  stages 
  

   in 
  the 
  insect 
  and 
  the 
  fishes 
  up 
  to 
  this 
  point 
  correspond, 
  

   and 
  consequently 
  it 
  became 
  at 
  once 
  suggested 
  to 
  us 
  that 
  

   probably 
  these 
  and 
  the 
  subsequent 
  stages 
  among 
  the 
  verte- 
  

   brates 
  had 
  been 
  misinterpreted. 
  

  

  A 
  careful 
  review 
  of 
  the 
  ensuing 
  stages 
  among 
  elasmo- 
  

   branchs 
  has 
  convinced 
  us 
  that 
  this 
  supposition 
  is 
  correct 
  ; 
  and 
  

   that 
  for 
  all 
  practical 
  purposes 
  the 
  later 
  stages 
  in 
  the 
  first 
  maiotic 
  

  

  