﻿64 
  W. 
  B. 
  IJANDLES. 
  

  

  moreover, 
  the 
  epipodial 
  nerve 
  has 
  come 
  away 
  intact 
  with 
  the 
  

   pleural 
  portion 
  of 
  the 
  cord, 
  while 
  those 
  nerves 
  distributed 
  

   to 
  the 
  foot 
  have 
  remained 
  on 
  the 
  pedal 
  half. 
  

  

  Boutan 
  also 
  supports 
  the 
  theory 
  of 
  the 
  double 
  nature 
  of 
  the 
  

   pedal 
  cord 
  from 
  his 
  investigations 
  on 
  the 
  anatomy 
  of 
  Fis- 
  

   surella 
  (3) 
  and 
  Parmophorous 
  (4). 
  In 
  the 
  latter 
  genus 
  he 
  

   distinguishes 
  three 
  kinds 
  of 
  nerves 
  given 
  off 
  from 
  the 
  ventral 
  

   nerve-cord 
  : 
  (1) 
  from 
  the 
  lower 
  surface, 
  nerves 
  which 
  go 
  

   exclusively 
  to 
  the 
  foot; 
  (2) 
  laterally, 
  nerves 
  distributed 
  to 
  the 
  

   collarette, 
  i. 
  e. 
  the 
  epipodium 
  or 
  inferior 
  mantle 
  ; 
  (3) 
  between 
  

   these 
  latter, 
  nerves 
  which 
  go 
  directly 
  to 
  the 
  mantle 
  ; 
  thus 
  both 
  

   pedal 
  and 
  pleural 
  nerves 
  are 
  given 
  off 
  from 
  the 
  lower 
  and 
  

   upper 
  halves 
  respectively 
  of 
  the 
  ventral 
  nerve-cord. 
  

  

  Bouvier 
  and 
  Fischer 
  (8) 
  also 
  regard 
  these 
  nerve 
  -cords 
  as 
  

   consisting 
  of 
  pleural 
  and 
  pedal 
  halves 
  and 
  the 
  epipodium 
  as 
  

   a 
  pallial 
  structure; 
  they, 
  however, 
  consider 
  that 
  many 
  of 
  the 
  

   nerves 
  given 
  off 
  from 
  these 
  cords 
  contain 
  fibres 
  from 
  both 
  

   pleural 
  and 
  pedal 
  halves, 
  that 
  these 
  nerves 
  in 
  fact 
  consist 
  of 
  

   mixed 
  fibres. 
  

  

  If, 
  however, 
  the 
  ventral 
  nerve-cords 
  are 
  purely 
  pedal, 
  as 
  

   Spengel 
  and 
  others 
  maintain, 
  it 
  is 
  obvious 
  that 
  the 
  epipodium, 
  

   being 
  innervated 
  from 
  a 
  pedal 
  centre, 
  must 
  be 
  regarded 
  as 
  an 
  

   outgrowth 
  of 
  the 
  foot, 
  having 
  no 
  connection 
  whatever 
  with 
  

   the 
  mantle. 
  

  

  Arguments 
  in 
  favour 
  of 
  this 
  view 
  are 
  based 
  upon 
  histo- 
  

   logical 
  investigations. 
  Haller 
  (20) 
  finds 
  that 
  in 
  Turbo 
  nerve- 
  

   fibres 
  pass 
  from 
  the 
  upper 
  to 
  the 
  lower 
  portion 
  of 
  the 
  ventral 
  

   nerve-cord. 
  Again, 
  Woodward 
  (45) 
  finds 
  the 
  same 
  condition 
  

   obtaining 
  in 
  Pie 
  urotom 
  aria. 
  Pelseneer, 
  who 
  has 
  always 
  

   maintained 
  that 
  the 
  epipodium 
  is 
  a 
  pedal 
  structure, 
  and 
  that 
  

   the 
  ventral 
  nerve-cords 
  are 
  entirely 
  pedal, 
  has 
  recently 
  

   (36, 
  p. 
  49) 
  shown 
  that 
  the 
  epipodial 
  nerves 
  receive 
  fibres 
  

   from 
  both 
  u])per 
  and 
  lower 
  halves 
  of 
  the 
  nerve-cords. 
  From 
  

   the 
  examination 
  of 
  numerous 
  serial 
  sections, 
  both 
  transverse 
  

   and 
  longitudinal, 
  of 
  various 
  species 
  of 
  Trochus 
  I 
  have 
  been 
  

   able 
  to 
  confirm 
  this 
  observation 
  of 
  Pelseneer's, 
  and 
  find 
  that 
  

   the 
  nerves 
  going 
  to 
  the 
  epipodium 
  have 
  a 
  double 
  origin 
  

  

  