﻿40 
  W. 
  B. 
  RANDLRS. 
  

  

  Similarly 
  inodified 
  areas 
  occur 
  on 
  the 
  dorsal 
  surface 
  of 
  the 
  

   foot 
  of 
  Pleurotomaria 
  (45, 
  p. 
  219), 
  and 
  Haliotis 
  (44, 
  pp. 
  

   335, 
  336). 
  This 
  specialised 
  area 
  is 
  undoubtedly 
  glandular 
  in 
  

   nature, 
  as, 
  when 
  microscopically 
  examined 
  in 
  section, 
  numerous 
  

   goblet-cells 
  are 
  seen 
  to 
  exist. 
  The 
  epithelium 
  covering 
  the 
  

   folds 
  of 
  the 
  grooves 
  consists 
  of 
  large 
  cylindrical, 
  ciliated 
  cells 
  

   with 
  granular 
  contents 
  and 
  large 
  rod-shaped 
  nuclei. 
  Inter- 
  

   spersed 
  between 
  the 
  ciliated 
  cells 
  are 
  mucous-discharging 
  

   goblet-cells. 
  Underneath 
  this 
  specialised 
  area 
  of 
  the 
  foot 
  

   the 
  various 
  blood-sinuses 
  are 
  particularly 
  large 
  and 
  numerous. 
  

   No 
  definite 
  function 
  has 
  as 
  yet 
  been 
  assigned 
  to 
  this 
  organ, 
  

   though 
  it 
  is 
  without 
  doubt 
  in 
  part 
  a 
  mucous 
  gland; 
  and 
  

   Wegmann 
  (44) 
  has 
  observed 
  in 
  living 
  specimens 
  of 
  Haliotis 
  

   the 
  secretion 
  of 
  a 
  mucous 
  thread 
  from 
  this 
  area. 
  On 
  the 
  

   autero-dorsal 
  surface 
  of 
  the 
  foot 
  is 
  situated 
  the 
  opercular 
  lobe 
  

   (figs. 
  8, 
  0, 
  op. 
  I.), 
  which 
  is 
  bean 
  shaped, 
  having 
  its 
  posterior 
  

   margin 
  free. 
  

  

  The 
  ciliation 
  which 
  is 
  so 
  marked 
  on 
  the 
  cephalic 
  tentacles 
  

   is 
  continued 
  over 
  the 
  great 
  part 
  of 
  the 
  foot, 
  the 
  cilia 
  on 
  the 
  

   margin 
  of 
  the 
  foot 
  being 
  especially 
  long 
  (fig. 
  7). 
  

  

  The 
  epi 
  podium 
  is 
  well 
  developed 
  in 
  the 
  Trochidfe, 
  

   though 
  more 
  conspicuously 
  so 
  in 
  the 
  members 
  of 
  the 
  sub- 
  

   genus 
  Gil)bu]a 
  than 
  in 
  those 
  of 
  the 
  Calliostomas. 
  It 
  

   originates 
  close 
  to 
  the 
  ocular 
  peduncle 
  (figs. 
  5, 
  6, 
  op. 
  c.) 
  and 
  

   extends 
  to 
  the 
  posterior 
  limit 
  of 
  the 
  foot, 
  attaining 
  its 
  

   maximum 
  development 
  in 
  the 
  region 
  of 
  the 
  neck, 
  where 
  it 
  

   enlarges 
  into 
  a 
  cervical 
  lobe 
  (ep. 
  r.) 
  In 
  the 
  species 
  of 
  

   Gibbula 
  the 
  cervical 
  lobes 
  are 
  asymmetrical, 
  the 
  right 
  

   being 
  larger 
  than 
  the 
  left 
  and 
  having 
  its 
  free 
  margin 
  entire, 
  

   while 
  the 
  margin 
  of 
  the 
  left 
  lobe 
  is 
  digitate 
  and 
  covered 
  with 
  

   sensory 
  papillfe. 
  This 
  fringing 
  of 
  the 
  left 
  cervical 
  lobe 
  is 
  

   very 
  conspicuous 
  in 
  T. 
  lineatus 
  (fig. 
  7, 
  ep. 
  c), 
  also 
  

   in 
  T. 
  cinerarius 
  and 
  T. 
  umbilicatus, 
  whereas 
  in 
  

   T. 
  magus, 
  though 
  the 
  right 
  and 
  left 
  lobes 
  are 
  asymmetrical 
  

   as 
  regards 
  actual 
  size, 
  the 
  fringing 
  of 
  the 
  left 
  is 
  by 
  no 
  means 
  

   so 
  obvious 
  as 
  in 
  the 
  preceding 
  species, 
  in 
  some 
  specimens 
  

   scarcely 
  any 
  trace 
  of 
  uneveuness 
  in 
  marginal 
  outline 
  being 
  

  

  