﻿ANATOMY 
  AND 
  AFFINITIES 
  OF 
  THE 
  TROCHTDyE. 
  61 
  

  

  and 
  the 
  columella 
  muscle 
  until 
  it 
  reaches 
  the 
  aforementioned 
  

   abdominal 
  ganglion. 
  There 
  is 
  no 
  trace 
  of 
  a 
  subintestinal 
  

   ganglion, 
  and 
  neither 
  by 
  the 
  method 
  of 
  dissection 
  nor 
  by 
  the 
  

   examination 
  of 
  serial 
  sections 
  have 
  I 
  been 
  able 
  to 
  make 
  out 
  

   any 
  trace 
  of 
  an 
  anastomosis 
  between 
  the 
  subintestinal 
  nerve 
  

   and 
  the 
  right 
  pallial 
  nerve, 
  though 
  such 
  a 
  connection 
  has 
  been 
  

   indicated 
  by 
  Bouvier 
  (8, 
  p. 
  171, 
  fig. 
  D). 
  

  

  The 
  common 
  origin 
  of 
  the 
  subintestinal 
  branch 
  of 
  the 
  

   visceral 
  commissure 
  with 
  the 
  left 
  pallial 
  nerve 
  does 
  not 
  

   appear 
  to 
  have 
  any 
  special 
  morphological 
  significance, 
  as 
  in 
  

   one 
  specimen 
  of 
  T. 
  cinerari 
  us, 
  the 
  nervous 
  system 
  of 
  which 
  

   was 
  modelled 
  in 
  wax 
  from 
  serial 
  sections, 
  exactly 
  the 
  reverse 
  

   condition 
  obtained, 
  the 
  supra-intestinal 
  nerve 
  and 
  the 
  right 
  

   pallial 
  nerve 
  having 
  a 
  common 
  origin 
  from 
  the 
  pleural 
  

   ganglion, 
  the 
  subintestinal 
  branch 
  arising 
  in 
  front 
  of 
  the 
  

   left 
  pallial 
  nerve. 
  

  

  The 
  abdominal 
  ganglion 
  {ab. 
  g.) 
  gives 
  origin 
  to 
  three 
  im- 
  

   portant 
  nerves. 
  One 
  arising 
  anteriorly 
  is 
  distributed 
  to 
  the 
  

   rectum, 
  a 
  median 
  large 
  branch, 
  the 
  visceral 
  nerve 
  {v.n.), 
  

   runs 
  along 
  the 
  inside 
  of 
  the 
  visceral 
  spire 
  and 
  innervates 
  the 
  

   stomach, 
  liver, 
  and 
  genital 
  gland, 
  while 
  the 
  third 
  nerve 
  is 
  dis- 
  

   tributed 
  to 
  the 
  right 
  kidney 
  and 
  heart. 
  

  

  The 
  visceral 
  loop 
  in 
  Trochus 
  is 
  typically 
  streptoueurous. 
  

  

  The 
  ventral 
  or 
  pedal 
  nerve 
  -cords 
  (figs. 
  30, 
  40, 
  

   pd. 
  c.) 
  are 
  paired 
  structures 
  running 
  in 
  the 
  muscular 
  mass 
  of 
  

   the 
  foot 
  throughout 
  its 
  entire 
  length. 
  On 
  their 
  outer 
  lateral 
  

   surfaces 
  they 
  are 
  superficially 
  divided 
  into 
  halves 
  by 
  a 
  longi- 
  

   tudinal 
  groove 
  (fig. 
  40). 
  At 
  the 
  anterior 
  end 
  of 
  the 
  foot 
  

   these 
  cords 
  approximate 
  one 
  another 
  closely, 
  and 
  are 
  united 
  

   b}^ 
  a 
  thick 
  anterior 
  pedal 
  commissure. 
  As 
  they 
  proceed 
  

   through 
  the 
  muscle 
  of 
  the 
  foot 
  they 
  diverge 
  slightly, 
  being 
  

   furthest 
  apart 
  at 
  their 
  middle 
  portion, 
  and 
  begin 
  to 
  converge 
  

   again 
  as 
  the 
  posterior 
  end 
  of 
  the 
  foot 
  is 
  reached. 
  

  

  In 
  addition 
  to 
  the 
  thick 
  anterior 
  pedal 
  commissure 
  there 
  

   are 
  numerous 
  thin 
  transverse 
  commissures 
  joining 
  the 
  pedal 
  

   cords 
  together, 
  and 
  giving 
  to 
  them 
  their 
  characteristic 
  

   scalariform 
  appearance. 
  Ganglion-cells 
  are 
  distributed 
  evenly 
  

  

  