﻿544 
  J. 
  BHETLAND 
  PARMER 
  AND 
  J. 
  E. 
  S. 
  MOORE. 
  

  

  other 
  instances 
  from 
  which 
  it 
  is 
  more 
  natural 
  to 
  draw 
  a 
  some- 
  

   what 
  different 
  inference. 
  In 
  the 
  cockroach, 
  for 
  example, 
  the 
  

   chromosomes 
  of 
  the 
  pre-maiotic 
  mitoses 
  do 
  not 
  originate 
  

   through 
  the 
  breaking 
  up 
  of 
  a 
  coiled 
  spirem 
  filament. 
  For 
  

   in 
  this 
  example 
  it 
  is 
  usually 
  possible 
  to 
  see 
  the 
  limits 
  of 
  the 
  

   individual 
  chromosome 
  even 
  when 
  the 
  nucleus 
  is 
  in 
  a 
  con- 
  

   dition 
  indistinguishable 
  from 
  the 
  rest. 
  The 
  primordia 
  (or 
  

   " 
  anlagen 
  ^') 
  of 
  each 
  future 
  chromatic 
  element 
  first 
  become 
  

   discernible 
  in 
  the 
  form 
  of 
  a 
  slight 
  chromatic 
  condensation. 
  

   At 
  such 
  a 
  time 
  the 
  linin 
  masses 
  which 
  will 
  be 
  involved 
  in 
  the 
  

   future 
  chromosomes 
  appear 
  always 
  to 
  be 
  visibly 
  discrete 
  and 
  

   separated 
  from 
  one 
  another. 
  The 
  more 
  or 
  less 
  completely 
  

   resting 
  aspect 
  of 
  the 
  cell 
  is 
  produced 
  by 
  the 
  linin 
  framework 
  

   of 
  each 
  chromosome 
  possessing 
  an 
  alveolar 
  or 
  reticular 
  struc- 
  

   ture 
  in 
  which 
  the 
  chromatin 
  is 
  irregulai'ly 
  distributed. 
  The 
  

   evolution 
  of 
  the 
  chromosomes 
  is 
  brought 
  about 
  by 
  the 
  separa- 
  

   tion 
  and 
  condensation 
  of 
  each 
  vesicular 
  linin 
  element, 
  and 
  the 
  

   chromatin 
  granules 
  become 
  eventually 
  closely 
  packed 
  together 
  

   within 
  the 
  axis 
  of 
  each 
  condensing 
  element. 
  A 
  somewhat 
  

   similar 
  state 
  of 
  affairs 
  has 
  been 
  observed 
  in 
  the 
  somatic 
  pro- 
  

   phases 
  in 
  Drosera 
  and 
  in 
  Tradescantia, 
  and 
  in 
  all 
  these 
  

   instances 
  it 
  would 
  seem 
  that 
  it 
  is 
  not 
  strictly 
  accurate 
  to 
  

   assume 
  that 
  the 
  chromosomes 
  originate 
  through 
  the 
  breaking 
  

   up 
  of 
  a 
  spirem 
  filament 
  ; 
  for 
  in 
  none 
  of 
  them 
  is 
  the 
  spirem, 
  

   as 
  generally 
  understood, 
  produced 
  in 
  the 
  first 
  instance, 
  and 
  

   in 
  Blatta 
  it 
  is 
  never 
  formed 
  at 
  all. 
  

  

  The 
  facts 
  revealed 
  by 
  the 
  above 
  instances 
  are 
  not 
  without 
  

   theoretical 
  importance. 
  They 
  strongly 
  favour 
  the 
  hypothesis 
  

   of 
  the 
  persistent 
  identity 
  of 
  the 
  chromosomes 
  from 
  generation 
  

   to 
  generation, 
  and 
  it 
  is 
  not 
  impossible 
  that 
  they 
  show 
  more 
  

   clearly 
  than 
  the 
  commoner 
  types 
  of 
  cells 
  the 
  manner 
  in 
  which 
  

   the 
  chromatic 
  elements 
  become 
  obscured 
  during 
  rest 
  and 
  re- 
  

   appear 
  at 
  each 
  succeeding 
  divisional 
  prophase. 
  For 
  example, 
  

   when, 
  as 
  usually 
  is 
  the 
  case, 
  the 
  somatic 
  chromosomes 
  

   are 
  relatively 
  very 
  long, 
  thin, 
  rod-like 
  structures, 
  if 
  these 
  

   persist 
  as 
  vesicnlated 
  masses 
  within 
  the 
  resting 
  cell 
  their 
  

   existence 
  would 
  not 
  generally 
  be 
  evident 
  owing 
  to 
  the 
  dis- 
  

  

  