﻿SPERMATOGENESIS 
  OF 
  PERIPLANETA 
  AMEKICANA. 
  579 
  

  

  The 
  degeneration 
  of 
  the 
  cytoplasm 
  takes 
  phicc 
  before 
  the 
  

   spermatozoa 
  can 
  mature, 
  and 
  these 
  pass 
  through 
  their 
  final 
  

   metamorphoses 
  suspended 
  in 
  dense 
  masses 
  in 
  the 
  grumous 
  

   liquid 
  derived 
  from 
  the 
  degenerated 
  cytoplasm. 
  

  

  Conclusion, 
  — 
  As 
  will 
  have 
  been 
  seen 
  from 
  the 
  preceding- 
  

   description, 
  the 
  behaviour 
  of 
  the 
  nucleolus 
  in 
  the 
  different 
  

   stages 
  of 
  spermatogenesis 
  of 
  P. 
  americana 
  is 
  distinctly 
  

   interesting 
  on 
  account 
  of 
  the 
  wide 
  difference 
  in 
  its 
  behaviour 
  

   from 
  that 
  ascribed 
  to 
  similar 
  structures 
  by 
  various 
  authors 
  in 
  

   other 
  animals. 
  We 
  find 
  it, 
  in 
  fact, 
  frequently 
  discussed 
  as 
  

   an 
  "accessory 
  chromosome," 
  differing 
  from 
  the 
  ordinary 
  

   chromosome 
  both 
  in 
  structure 
  and 
  function. 
  

  

  In 
  the 
  somatic 
  cell 
  the 
  nucleolus 
  does 
  not 
  persist 
  after 
  the 
  

   appearance 
  of 
  the 
  spindle, 
  but 
  undergoes 
  fragmentation, 
  and 
  

   is 
  thrown 
  out 
  into 
  the 
  cytoplasm, 
  where 
  it 
  undergoes 
  

   degeneration. 
  This 
  process 
  occurs 
  in 
  each 
  successive 
  somatic 
  

   division, 
  a 
  nucleolus 
  arising, 
  de 
  novo, 
  in 
  each 
  of 
  the 
  daughter 
  

   nuclei 
  resulting 
  from 
  such 
  division. 
  

  

  The 
  operations 
  described 
  by 
  Sutton 
  as 
  occurring 
  in 
  

   Brachystola 
  ('Kan. 
  Univ. 
  Quart,,' 
  vol. 
  ix, 
  No. 
  2, 
  1900), 
  and 
  

   by 
  Miss 
  Wallace, 
  in 
  Spiders 
  (' 
  Anat. 
  Auz.,' 
  Bd. 
  xviii, 
  Nos. 
  13 
  

   and 
  14), 
  do 
  not 
  occur 
  in 
  the 
  typical 
  insect 
  Ave 
  have 
  studied. 
  

  

  The 
  nucleolus 
  of 
  the 
  heterotype 
  cell 
  is 
  not 
  derived 
  from 
  

   that 
  of 
  the 
  immediately 
  preceding 
  somatic 
  cell, 
  but 
  arises 
  

   anew 
  in 
  the 
  earliest 
  condition 
  of 
  the 
  heterotype 
  stage. 
  

  

  But 
  in 
  such 
  cells 
  essentially 
  the 
  same 
  phenomena 
  are 
  

   repeated. 
  The 
  alteration 
  in 
  form 
  of 
  the 
  nucleolus, 
  in 
  this 
  

   case, 
  appears 
  to 
  be 
  due 
  solely 
  to 
  the 
  mechanical 
  influences 
  

   brought 
  to 
  bear 
  upon 
  an 
  elastic 
  structure 
  enclosed 
  in 
  a 
  

   nucleus, 
  the 
  contents 
  of 
  which 
  are 
  in 
  a 
  state 
  of 
  strain. 
  

   Immediately 
  this 
  strain 
  is 
  relieved 
  the 
  nucleolus 
  returns 
  to 
  

   its 
  original 
  spherical 
  condition. 
  With 
  regard 
  to 
  the 
  bifid 
  

   condition 
  of 
  the 
  nucleolus 
  of 
  the 
  heterotype 
  cell 
  in 
  its 
  early 
  

   stages, 
  this 
  is 
  probably 
  only 
  an 
  early 
  manifestation 
  of 
  a 
  

   tendency 
  to 
  division, 
  such 
  as 
  occurs 
  in 
  the 
  spermatid, 
  

   analogous 
  to 
  the 
  futile 
  development 
  of 
  a 
  flagellum 
  in 
  the 
  

  

  