﻿160 
  

  

  Mr. 
  C. 
  F. 
  U. 
  Meek. 
  

  

  or 
  enabling 
  me 
  thus 
  to 
  study 
  them, 
  and 
  for 
  permitting 
  me 
  to 
  publish 
  photo- 
  

   micrographs 
  that 
  I 
  made 
  at 
  the 
  time. 
  This 
  work 
  was 
  laid 
  aside 
  in 
  September, 
  

   1914, 
  and 
  I 
  have 
  been 
  unable 
  to 
  resume 
  it 
  until 
  this 
  year 
  (1919). 
  

  

  I 
  now 
  intend 
  to 
  give 
  these 
  and 
  other 
  results. 
  The 
  evidence 
  produced 
  will 
  

   be 
  supported 
  by 
  photo-micrographs 
  in 
  which 
  the 
  differences 
  in 
  chromatin 
  

   volume 
  and 
  chromosome 
  diameter 
  are 
  distinct 
  enough 
  to 
  be 
  recognised 
  without 
  

   recourse 
  to 
  actual 
  measurements. 
  These 
  photo-micrographs 
  have 
  been 
  taken 
  

   from 
  several 
  hundreds 
  that 
  I 
  have 
  made, 
  representing 
  many 
  different 
  animals,, 
  

   and 
  will 
  be 
  found 
  completely 
  to 
  disprove 
  the 
  third 
  and 
  modified 
  fourth 
  

   generalisations. 
  

  

  Material 
  and 
  Methods. 
  

  

  All 
  material, 
  except 
  that 
  of 
  Felis, 
  was 
  prepared 
  either 
  by 
  me 
  or 
  by 
  my 
  

   assistant, 
  Mr. 
  T. 
  Russell 
  Goddard. 
  

  

  The 
  testes 
  were 
  preserved 
  in 
  Flemming's 
  strong 
  chromo-aceto-osmic 
  acid 
  

   fluid, 
  in 
  which 
  they 
  remained 
  for 
  24 
  hours. 
  They 
  were 
  then 
  thoroughly 
  

   washed 
  in 
  running 
  water, 
  and 
  passed 
  through 
  successive 
  strengths 
  of 
  alcohol 
  : 
  

   and, 
  after 
  being 
  cleared 
  in 
  xylol, 
  were 
  embedded 
  in 
  paraffin. 
  Sections 
  were 
  

   cut 
  8^, 
  thick 
  with 
  a 
  Cambridge 
  rocking 
  microtome, 
  and 
  were 
  stained 
  on 
  the 
  

   slide. 
  The 
  slides 
  were 
  placed 
  for 
  four 
  to 
  six 
  hours 
  in 
  an 
  aqueous 
  solution 
  of 
  

   ferric 
  alum, 
  and 
  were 
  then 
  stained 
  for 
  12 
  to 
  14 
  hours 
  in 
  Heidenhain's 
  iron 
  

   hematoxylin. 
  

  

  The 
  preparations 
  were 
  studied 
  with 
  a 
  Zeiss 
  apochromatic 
  oil-immersion 
  

   objective 
  of 
  2 
  mm. 
  focus 
  and 
  N.A. 
  l 
  - 
  30, 
  and 
  the 
  various 
  compensating 
  oculars. 
  

   The 
  light 
  was 
  obtained 
  from 
  an 
  inverted 
  incandescent 
  gas 
  lamp, 
  and 
  was 
  

   passed 
  through 
  a 
  Watson 
  holoscopic 
  oil-immersion 
  substage 
  condenser. 
  All 
  

   photo-micrographs 
  were 
  made 
  at 
  the 
  same 
  magnification 
  with 
  a 
  Zeiss 
  camera, 
  

   the 
  objective 
  mentioned 
  above, 
  and 
  compensating 
  ocular 
  No. 
  4. 
  

  

  Chromatin 
  Volume 
  and 
  Chromosome 
  Diameter. 
  

  

  Figs. 
  1 
  to 
  4 
  of 
  the 
  Plate 
  represent 
  the 
  grasshopper, 
  Stenohothrus 
  viridulus. 
  

   Fig. 
  1 
  shows 
  a 
  polar 
  view 
  of 
  the 
  spermatogonial 
  metaphase. 
  Fig. 
  2 
  shows 
  a 
  

   polar 
  view 
  of 
  the 
  primary 
  spermatocyte 
  metaphase 
  ; 
  while 
  fig. 
  3 
  shows 
  a 
  

   lateral 
  view 
  of 
  this 
  metaphase, 
  and 
  the 
  odd 
  or 
  heterotropic 
  chromosome 
  

   is 
  seen 
  passing 
  undivided 
  to 
  one 
  pole. 
  Fig. 
  4 
  shows 
  a 
  polar 
  view 
  of 
  the 
  

   secondary 
  spermatocyte 
  metaphase. 
  A 
  reference 
  to 
  my 
  first 
  paper 
  and 
  to- 
  

   papers 
  of 
  other 
  cytologists 
  will 
  prove 
  that 
  these 
  photomicrographs 
  are 
  typical 
  

   both 
  of 
  this 
  species 
  and 
  of 
  other 
  closely 
  allied 
  animals. 
  

  

  Figs. 
  5 
  to 
  11 
  represent 
  the 
  moth, 
  Smerinthus 
  populi. 
  Fig. 
  5 
  shows 
  a 
  polar 
  

   view 
  of 
  the 
  spermatogonial 
  metaphase. 
  Fig. 
  6 
  shows 
  lateral 
  views 
  of 
  this 
  

   metaphase 
  ; 
  and 
  a 
  lateral 
  view 
  of 
  the 
  early 
  anaphase 
  is 
  shown 
  in 
  fig. 
  7. 
  

  

  