﻿108 
  E. 
  J. 
  ALLEN. 
  

  

  By 
  means 
  of 
  the 
  muscular 
  system 
  just 
  described, 
  assisted 
  by 
  

   tlie 
  larger 
  muscles 
  {muse.) 
  attached 
  to 
  the 
  apex 
  of 
  the 
  organ, 
  

   not 
  ouly 
  can 
  the 
  whole 
  organ 
  be 
  withdrawn 
  to 
  a 
  certain 
  extent 
  

   within 
  the 
  body, 
  but 
  the 
  hair-bearing 
  area 
  and 
  its 
  rim 
  can 
  be 
  

   at 
  the 
  same 
  time 
  still 
  farther 
  withdrawn^ 
  until 
  the 
  external 
  

   appearance 
  of 
  the 
  organ 
  is 
  little 
  more 
  than 
  that 
  of 
  a 
  pore 
  with 
  

   a 
  number 
  of 
  hairs 
  protruding 
  through 
  it. 
  

  

  The 
  hair 
  -bearing 
  cells 
  are 
  represented 
  in 
  figs. 
  34 
  and 
  36. 
  

   The 
  exact 
  outlines 
  of 
  the 
  individual 
  cells 
  are 
  not 
  marked 
  out 
  

   in 
  any 
  of 
  the 
  preparations, 
  and 
  the 
  meaning 
  of 
  the 
  appearances 
  

   shown 
  is 
  therefore 
  not 
  quite 
  clear. 
  The 
  great 
  resemblance 
  

   between 
  these 
  appearances 
  and 
  those 
  shown 
  by 
  the 
  ciliated 
  

   cells 
  of 
  the 
  nuchal 
  groove 
  (PI. 
  11, 
  figs. 
  40 
  and 
  41) 
  and 
  of 
  the 
  

   intestinal 
  epithelium 
  (PI. 
  11, 
  fig. 
  44) 
  gives, 
  however, 
  an 
  

   important 
  clue 
  to 
  their 
  interpretation. 
  

  

  Immediately 
  under 
  the 
  external 
  layer 
  of 
  cuticle 
  is 
  an 
  un- 
  

   stained 
  space 
  or 
  layer 
  of 
  unstained 
  protoplasm,^ 
  through 
  

   which 
  the 
  inner 
  ends 
  of 
  the 
  sensory 
  hairs 
  can 
  be 
  seen 
  to 
  pass 
  

   just 
  as 
  in 
  the 
  ciliated 
  cells 
  of 
  the 
  nuchal 
  organ 
  (cf. 
  p. 
  114) 
  

   and 
  of 
  the 
  oesophagus 
  (p. 
  117). 
  

  

  Then 
  follows 
  a 
  layer 
  of 
  deeply 
  staining 
  short 
  rods 
  (figs. 
  34 
  

   and 
  36 
  s. 
  v.), 
  which 
  is 
  succeeded 
  by 
  a 
  layer 
  of 
  faintly 
  staining 
  

   long 
  rods 
  {l.r.), 
  just 
  as 
  in 
  the 
  ciliated 
  cells. 
  The 
  only 
  

   difference 
  exhibited 
  in 
  the 
  two 
  cases 
  up 
  to 
  this 
  point 
  is 
  that 
  

   the 
  hairs, 
  in 
  their 
  course 
  through 
  the 
  clear 
  space 
  between 
  the 
  

   cuticle 
  and 
  the 
  line 
  of 
  short 
  rods, 
  stain 
  somewhat 
  deeply 
  

   immediately 
  below 
  the 
  cuticle, 
  red 
  in 
  methyl-blue-eosiu 
  

   preparations 
  like 
  the 
  short 
  rods 
  themselves, 
  producing 
  the 
  

   appearance 
  of 
  a 
  secondary 
  layer 
  of 
  short 
  rods 
  (fig. 
  36, 
  s. 
  r. 
  2), 
  

   which, 
  however, 
  is 
  vei'y 
  much 
  less 
  marked 
  than 
  the 
  main 
  

   layer. 
  This 
  layer 
  occupies 
  a 
  similar 
  position 
  to 
  the 
  layer 
  of 
  

   " 
  bulbi 
  " 
  of 
  ciliated 
  cells, 
  which 
  are 
  further 
  referred 
  to 
  on 
  

   p. 
  118. 
  

  

  The 
  short 
  rods, 
  as 
  in 
  the 
  ciliated 
  cells, 
  stain 
  bright 
  red 
  in 
  

  

  1 
  It 
  is 
  possible 
  that 
  the 
  size 
  of 
  this 
  space 
  may 
  be 
  exaggerated 
  by 
  contraction 
  

   of 
  the 
  protoplasm 
  of 
  the 
  cells 
  caused 
  by 
  the 
  reagents 
  employed. 
  In 
  that 
  case 
  

   the 
  layer 
  of 
  short 
  rods 
  would 
  lie 
  closer 
  to 
  the 
  cuticle. 
  

  

  