﻿96 
  E. 
  J. 
  ALLEN. 
  

  

  projecting 
  to 
  an 
  equal 
  extent 
  externally 
  beyond 
  the 
  surface 
  

   of 
  the 
  papilla 
  and 
  internally 
  into 
  the 
  protoplasm 
  of 
  the 
  gland- 
  

   cells. 
  

  

  On 
  account 
  of 
  the 
  flattened 
  nature 
  of 
  the 
  epithelium, 
  the 
  

   gland-cells, 
  which 
  ai-e 
  easily 
  distinguished 
  by 
  their 
  more 
  deeply 
  

   staining 
  protoplasm, 
  do 
  not 
  lie 
  immediately 
  beneath 
  the 
  

   tubercle, 
  but 
  are 
  drawn 
  considerably 
  to 
  one 
  side. 
  The 
  nucleus 
  

   of 
  each 
  gland-cell 
  lies 
  near 
  its 
  proximal 
  end. 
  It 
  is 
  much 
  

   smaller 
  than 
  the 
  nuclei 
  of 
  the 
  ordinary 
  epithelial 
  cells 
  sur- 
  

   rounding 
  it, 
  spherical 
  rather 
  than 
  oval 
  in 
  shape, 
  contains 
  a 
  

   large 
  quantity 
  of 
  chromatin 
  in 
  the 
  form 
  of 
  a 
  considerable 
  

   number 
  of 
  large, 
  deeply 
  staining 
  granules 
  of 
  about 
  equal 
  size, 
  

   and 
  is 
  thus 
  very 
  readily 
  distinguished 
  from 
  the 
  nuclei 
  of 
  the 
  

   epithelium. 
  Usually 
  three 
  or 
  four 
  such 
  nuclei 
  can 
  be 
  dis- 
  

   tinguished 
  lying 
  close 
  together 
  in 
  the 
  neighbourhood 
  of 
  the 
  

   base 
  of 
  each 
  of 
  the 
  chitinous 
  tubercles. 
  In 
  the 
  figure 
  (fig. 
  

   23) 
  only 
  one 
  such 
  nucleus 
  is 
  shown 
  ; 
  but 
  three 
  were 
  dis- 
  

   tinguished 
  in 
  the 
  sections, 
  two 
  lying 
  one 
  over 
  the 
  other, 
  in 
  

   the 
  section 
  from 
  which 
  the 
  figure 
  was 
  made, 
  and 
  one 
  in 
  the 
  

   following 
  section. 
  

  

  Scattered 
  over 
  the 
  ventral 
  surface 
  of 
  the 
  cuticle, 
  especially 
  

   in 
  the 
  anterior 
  segments 
  of 
  the 
  body, 
  a 
  number 
  of 
  rounded 
  

   tubercles 
  or 
  callosities 
  are 
  found. 
  A 
  section 
  through 
  two 
  of 
  

   these 
  is 
  shown 
  in 
  fig. 
  21 
  (PI. 
  9). 
  They 
  are 
  almost 
  entirely 
  

   cuticular 
  structures 
  [cal.), 
  the 
  epithelial 
  cells 
  only 
  protruding 
  

   for 
  a 
  very 
  short 
  distance 
  into 
  them. 
  The 
  internal, 
  lightly 
  

   staining 
  layer 
  of 
  the 
  cuticle 
  found 
  in 
  this 
  region 
  of 
  the 
  body, 
  

   though 
  curved 
  slightly 
  outwards, 
  is 
  little 
  if 
  at 
  all 
  thickened. 
  

   The 
  tubercle 
  is 
  chiefly 
  formed, 
  therefore, 
  by 
  a 
  great 
  thickening 
  

   of 
  the 
  outer 
  or 
  deeply 
  staining 
  layer 
  of 
  the 
  cuticle. 
  The 
  

   character 
  of 
  this 
  layer 
  seems 
  also 
  to 
  be 
  slightly 
  altered, 
  for 
  in 
  

   methyl-blue-eosin 
  preparations 
  it 
  takes 
  on 
  a 
  deep 
  reddish 
  or 
  

   purple 
  tint 
  rather 
  than 
  blue, 
  and 
  often 
  exhibits 
  a 
  character- 
  

   istic 
  radial 
  structure 
  due 
  to 
  a 
  number 
  of 
  deeply 
  staining, 
  

   radiating 
  bars 
  (fig. 
  21). 
  

  

  The 
  appearance 
  of 
  these 
  tubercles 
  at 
  once 
  brings 
  to 
  mind 
  

   those 
  upon 
  which 
  stand 
  the 
  tubes 
  of 
  the 
  gland-cells 
  already 
  

  

  