﻿5^0 
  J. 
  K. 
  S. 
  MOOKD 
  ANl) 
  L. 
  E. 
  UOBlNSON. 
  

  

  homotjle 
  cell 
  in 
  Elasmobrauchs 
  as 
  already 
  described 
  by 
  one 
  

   of 
  us 
  ('Quart. 
  Jouru. 
  Micr. 
  Sci./ 
  vol. 
  xlvi). 
  

  

  As 
  was 
  the 
  case 
  iu 
  tlie 
  somatic 
  period^ 
  the 
  nucleolus 
  of 
  the 
  

   heterotype 
  cell 
  undergoes 
  fragmentation 
  prior 
  to 
  the 
  division 
  

   of 
  the 
  cell, 
  and 
  being 
  extruded 
  from 
  the 
  nucleus, 
  undergoes 
  

   degeneration 
  in 
  the 
  cytoplasm. 
  

  

  This 
  nucleolus 
  is 
  undoubtedly 
  the 
  homologue 
  of 
  the 
  struc- 
  

   ture 
  described 
  by 
  McClung 
  as 
  the 
  " 
  accessory 
  chromosome 
  " 
  

   ('Zool. 
  Bull./ 
  vol. 
  ii, 
  1899); 
  by 
  Montgomery 
  in" 
  Pentatoma," 
  

   ('Zool. 
  Jalirb./ 
  Bd. 
  xii) 
  ; 
  and 
  by 
  Paulmier, 
  in 
  '' 
  Anasa 
  Tristis" 
  

   (' 
  Journ. 
  Morph./ 
  supplement 
  to 
  vol. 
  xv, 
  1899). 
  

  

  Toyama, 
  in 
  his 
  investigations 
  on 
  Bombyx, 
  and 
  other 
  

   Lepidoptera 
  (' 
  Bull. 
  Coll. 
  Agric, 
  Imp. 
  Univ. 
  Japan/ 
  vol. 
  ii), 
  

   describes 
  the 
  presence 
  of 
  two 
  nucleoli 
  iu 
  the 
  heterotype 
  

   nucleus, 
  both 
  of 
  which 
  are 
  cast 
  out 
  into 
  the 
  cytoplasm 
  to 
  

   undergo 
  degenerative 
  chauges. 
  Platrus, 
  in 
  his 
  work 
  on 
  

   Lepidoptera 
  {' 
  luteruat. 
  Monatschr. 
  fiir 
  Anat. 
  med. 
  Physiol./ 
  

   vol. 
  iii), 
  gives 
  nothing 
  very 
  detinite 
  in 
  his 
  description 
  of 
  the 
  

   nucleolus, 
  but 
  evidently 
  noticed 
  nothing 
  approaching 
  the 
  

   behaviour 
  of 
  a 
  chromosome 
  in 
  these 
  structures. 
  

  

  In 
  his 
  researches 
  upon 
  Caloptinin 
  femur 
  rubrumaud 
  

   Cicada 
  tibicen 
  ('Bull. 
  Imus. 
  Comp. 
  Zool., 
  Harvard 
  Univ.,' 
  

   vols, 
  xxvii, 
  xxix, 
  1895, 
  1896), 
  Wilson 
  describes 
  the 
  reaction 
  to 
  

   stains 
  of 
  the 
  different 
  nuclear 
  elements. 
  He 
  found 
  that 
  

   under 
  certain 
  conditions 
  the 
  nucleoli 
  stain 
  differently 
  to 
  the 
  

   chromosomes. 
  He 
  also 
  noticed 
  that 
  in 
  Cicada 
  the 
  nucleoli 
  

   in 
  the 
  heretotype 
  all 
  underwent 
  fission, 
  and 
  were 
  finally 
  

   extruded. 
  In 
  the 
  present 
  case 
  material 
  was 
  used 
  which 
  

   had 
  been 
  hxed 
  by 
  various 
  methods, 
  — 
  by 
  Plemming^s 
  Huid, 
  

   Hemann's 
  fluid, 
  corrosive 
  acetic, 
  Kabb's 
  method, 
  and 
  van 
  

   Hath. 
  It 
  was 
  stained 
  either 
  by 
  Flemming's 
  triple 
  method 
  or 
  

   Ueidenhain's 
  iron 
  hajmatoxyliu, 
  counterstained 
  with 
  Orange 
  

   G, 
  but 
  in 
  all 
  cases 
  the 
  nucleolus 
  was 
  stained 
  in 
  the 
  same 
  

   manner 
  as 
  the 
  chromatin. 
  

  

  The 
  nucleolus 
  of 
  the 
  spermatid 
  appears 
  to 
  be 
  differentiated 
  

   directly 
  from 
  the 
  chromatin 
  of 
  the 
  reconstructed 
  daughter 
  

   nucleus 
  immediately 
  after 
  the 
  homotype 
  division, 
  and 
  the 
  most 
  

   feasible 
  explanation 
  oi 
  the 
  process 
  which 
  follows 
  is, 
  that 
  it 
  is 
  

  

  