﻿THE 
  ANATOMY 
  OF 
  PCEOILOCHiETUS, 
  CLAPAREDE. 
  107 
  

  

  apex 
  of 
  the 
  organ^ 
  where 
  they 
  pass 
  into 
  the 
  large 
  muscles 
  

   attached 
  to 
  that 
  apex 
  (fig. 
  34^ 
  viusc.) 
  The 
  arrangement 
  of 
  

   these 
  muscle-bands 
  will 
  be 
  seen 
  on 
  comparing 
  the 
  three 
  

   figures 
  representing 
  respectively 
  a 
  horizontal 
  section 
  (fig. 
  34), 
  

   a 
  section 
  in 
  the 
  longitudinal-vertical 
  plane 
  of 
  the 
  animal, 
  and 
  

   therefore 
  parallel 
  to 
  the 
  hair-bearing 
  surface 
  of 
  the 
  organ 
  

   (fig. 
  38), 
  and 
  a 
  transverse 
  section 
  through 
  the 
  anterior 
  row 
  

   of 
  muscle-bands 
  (fig. 
  35). 
  From 
  figs. 
  34 
  and 
  38 
  especially 
  it 
  

   will 
  be 
  seen 
  that 
  along 
  the 
  anterior 
  margin 
  of 
  the 
  hair- 
  

   bearing 
  area 
  a 
  single 
  row 
  only 
  of 
  muscle-bands 
  exists, 
  that 
  

   along 
  the 
  dorsal 
  mai'gin 
  there 
  are 
  several 
  rows, 
  whilst 
  on 
  the 
  

   posterior 
  side 
  there 
  are 
  two 
  rows 
  with 
  a 
  narrow 
  strip 
  of 
  the 
  

   hair-bearing 
  area 
  between 
  them. 
  On 
  the 
  ventral 
  border 
  there 
  

   are 
  no 
  muscle-bands 
  at 
  all. 
  The 
  ends 
  of 
  the 
  muscle-bands 
  in 
  

   contact 
  with 
  the 
  cuticle 
  broaden 
  considerably, 
  so 
  that 
  the 
  

   surface 
  of 
  contact 
  between 
  the 
  bands 
  and 
  the 
  cuticle 
  is 
  greatly 
  

   enlarged 
  (figs. 
  34 
  and 
  35), 
  the 
  cuticle 
  itself 
  being 
  at 
  the 
  

   same 
  time 
  very 
  much 
  thickened 
  (fig. 
  35). 
  The 
  course 
  of 
  the 
  

   fibres 
  from 
  the 
  margin 
  of 
  the 
  hair-bearing 
  area 
  to 
  the 
  apex 
  

   of 
  the 
  organ 
  is 
  easily 
  demonstrated 
  in 
  a 
  series 
  of 
  horizontal 
  

   sections 
  such 
  as 
  fig. 
  34. 
  

  

  In 
  fig. 
  35, 
  which 
  represents 
  a 
  transverse 
  section 
  through 
  

   the 
  anterior 
  line 
  of 
  muscle-bands, 
  it 
  will 
  be 
  noticed 
  that 
  

   between 
  the 
  bands 
  a 
  row 
  of 
  rather 
  large, 
  oval 
  nuclei 
  exists. 
  

   It 
  is 
  not 
  clear 
  to 
  exactly 
  what 
  cells 
  these 
  nuclei 
  belong. 
  

   They 
  may 
  be 
  the 
  nuclei 
  of 
  the 
  muscle-bands, 
  in 
  which 
  case 
  

   each 
  band 
  would 
  be 
  morphologically 
  a 
  single 
  cell, 
  or 
  they 
  

   may 
  belong 
  to 
  a 
  series 
  of 
  ganglion-cells 
  of 
  a 
  similar 
  type 
  

   to 
  the 
  large 
  ganglion-cells 
  shown 
  in 
  figs. 
  30 
  and 
  37 
  (see 
  

   below). 
  

  

  Fig. 
  37 
  is 
  drawn 
  from 
  a 
  transverse 
  section 
  at 
  the 
  level 
  of 
  

   the 
  posterior 
  rows 
  of 
  muscle-bands. 
  

  

  In 
  addition 
  to 
  the 
  bands 
  already 
  described 
  a 
  number 
  of 
  

   single 
  muscle-fibres 
  pass 
  from 
  the 
  apex 
  of 
  the 
  organ 
  to 
  the 
  

   cuticle 
  in 
  the 
  region 
  posterior 
  to 
  the 
  raised 
  rim 
  of 
  the 
  hair- 
  

   bearing 
  area 
  ; 
  these 
  are 
  also 
  indicated 
  in 
  fig. 
  34. 
  All 
  these 
  

   muscle-bauds 
  and 
  fibres 
  stain 
  deeply 
  in 
  sections. 
  

  

  