﻿THE 
  ANATOMY 
  OF 
  PCEOlLOCHxETUS, 
  CLAPAKEDE. 
  103 
  

  

  postei'ior 
  end. 
  The 
  two 
  bundles 
  unite 
  to 
  form 
  a 
  stout 
  nerve, 
  

   which 
  runs 
  outwards 
  to 
  a 
  large 
  ganglion, 
  situated 
  at 
  the 
  base 
  

   of 
  the 
  palp, 
  the 
  palp-ganglion 
  (of. 
  PI. 
  10, 
  fig. 
  30). 
  The 
  nerve 
  

   of 
  the 
  palp-ganglion 
  thus 
  has 
  a 
  double 
  origin 
  in 
  the 
  brain. 
  

  

  From 
  the 
  posterior 
  end 
  of 
  the 
  brain, 
  fibres 
  also 
  pass 
  back- 
  

   wards 
  and 
  enter 
  the 
  nuchal 
  organ, 
  where 
  they 
  mingle 
  with 
  

   the 
  felt-work 
  o£ 
  fibres 
  of 
  a 
  large 
  ganglion 
  which 
  lies 
  in 
  the 
  

   base 
  of 
  that 
  organ 
  — 
  the 
  nuchal 
  ganglion 
  (fig. 
  42). 
  The 
  

   fibres 
  passing 
  from 
  the 
  brain 
  to 
  the 
  nuchal 
  organ 
  are 
  not 
  

   easy 
  to 
  demonstrate, 
  as 
  they 
  do 
  not 
  form 
  definite 
  nerve- 
  

   bundles, 
  but 
  rather 
  two 
  thin 
  sheets, 
  one 
  from 
  each 
  half 
  of 
  

   the 
  brain, 
  the 
  individual 
  fibres 
  of 
  which 
  pass 
  between 
  or 
  below 
  

   the 
  epithelial 
  cells 
  lying 
  at 
  the 
  junction 
  of 
  the 
  nuchal 
  organ 
  

   and 
  brain. 
  

  

  The 
  ganglion-cells 
  of 
  the 
  brain 
  form 
  an 
  almost 
  continuous 
  

   cap 
  covering 
  the 
  punctated 
  substance. 
  It 
  is, 
  however, 
  pos- 
  

   sible 
  to 
  distinguish 
  in 
  each 
  half 
  of 
  the 
  brain 
  an 
  anterior 
  group 
  

   of 
  cells 
  (Text-fig. 
  1, 
  ant. 
  gang, 
  cells), 
  the 
  fibres 
  from 
  which 
  

   unite 
  in 
  a 
  bundle, 
  which 
  is 
  directed 
  downwards 
  and 
  back- 
  

   wards 
  into 
  the 
  mass 
  of 
  punctated 
  substance 
  lying 
  below 
  that 
  

   region 
  (m. 
  h.), 
  where 
  the 
  oesophageal 
  commissures 
  take 
  origin. 
  

   The 
  further 
  fate 
  of 
  this 
  bundle 
  of 
  fibres 
  could 
  not 
  be 
  ascer- 
  

   tained, 
  but 
  a 
  comparison 
  with 
  transverse 
  sections 
  appears 
  to 
  

   suggest 
  that 
  it 
  may 
  cross 
  with 
  its 
  fellow 
  and 
  then 
  give 
  rise 
  to 
  

   the 
  anterior 
  root 
  of 
  the 
  palp-ganglion 
  nerve 
  {n. 
  j^. 
  1) 
  of 
  the 
  

   opposite 
  side. 
  

  

  A 
  number 
  oi^ 
  very 
  large 
  ganglion-cells 
  {post 
  gang, 
  cells), 
  

   situated 
  at 
  the 
  posterior 
  end 
  of 
  the 
  brain, 
  which 
  send 
  their 
  

   processes 
  into 
  the 
  general 
  mass 
  of 
  the 
  central 
  felt-work, 
  are 
  

   also 
  conspicuous. 
  These 
  cells, 
  however, 
  do 
  not 
  appear 
  to 
  

   constitute 
  a 
  definite 
  group, 
  but 
  grade 
  off 
  into 
  the 
  general 
  

   mass 
  of 
  ganglion-cells. 
  

  

  The 
  Palp-ganglia. 
  — 
  The 
  two 
  palp-ganglia 
  are 
  situated 
  at 
  

   some 
  distance 
  from 
  the 
  brain. 
  They 
  are 
  ganglia 
  of 
  considerable 
  

   size, 
  and 
  contain 
  large 
  ganglion- 
  cells, 
  as 
  well 
  as 
  a 
  nervous 
  felt- 
  

   work. 
  They 
  lie 
  one 
  on 
  each 
  side 
  of 
  the 
  body 
  at 
  the 
  base 
  of 
  

   the 
  palp 
  and 
  external 
  to 
  that 
  structure 
  (PI. 
  10, 
  fig. 
  30). 
  Each 
  

  

  