﻿124 
  PROCEEDINGS 
  OF 
  THE 
  MALACOLOGICAI, 
  SOCIEXT. 
  

  

  them 
  had 
  tails. 
  Each 
  had 
  an 
  oral 
  sucker 
  at 
  the 
  anterior 
  end, 
  and 
  

   a 
  ventral 
  sucker 
  of 
  about 
  the 
  same 
  size 
  just 
  in 
  front 
  of 
  the 
  centre 
  of 
  

   the 
  lower 
  surface. 
  Stained 
  specimens 
  showed 
  a 
  short 
  but 
  very 
  

   muscular 
  pharynx 
  behind 
  the 
  oral 
  sucker. 
  Posterior 
  to 
  this 
  the 
  

   greater 
  part 
  of 
  the 
  parasite 
  seemed 
  to 
  be 
  occupied 
  by 
  the 
  pair 
  of 
  

   enteric 
  ciEca, 
  which 
  appeared 
  to 
  be 
  unusually 
  large. 
  At 
  the 
  hind 
  

   end 
  a 
  very 
  small 
  vesicle 
  could 
  be 
  discerned 
  in 
  some 
  of 
  the 
  specimens 
  : 
  

   this 
  was 
  probably 
  the 
  excretory 
  bladder. 
  Along 
  the 
  centre 
  in 
  the 
  

   posterior 
  part 
  of 
  the 
  animal 
  there 
  were 
  some 
  darkly 
  staining 
  objects, 
  

   which 
  may 
  have 
  been 
  the 
  rudiments 
  of 
  the 
  reproductive 
  organs. 
  

   These 
  organs, 
  however, 
  would 
  not 
  be 
  likely 
  to 
  become 
  lully 
  

   developed 
  until 
  the 
  snail 
  had 
  been 
  eaten 
  by 
  some 
  bird 
  or 
  possibly 
  

   a 
  small 
  mammal, 
  and 
  the 
  parasite 
  thus 
  transfei'red 
  to 
  its 
  verte- 
  

   brate 
  host. 
  

  

  So 
  long 
  ago 
  as 
  1846 
  H. 
  Meckel 
  found 
  a 
  young 
  Trematode 
  or 
  

   Cercaria 
  in 
  the 
  kidney 
  of 
  Helix 
  pomatia,^ 
  and 
  in 
  1855 
  Pli. 
  de 
  Filippi 
  

   read 
  a 
  paper 
  before 
  the 
  Royal 
  Academy 
  of 
  Sciences 
  at 
  Turin 
  

   describing 
  a 
  form 
  which 
  he 
  had 
  found 
  in 
  IT. 
  aspersa, 
  and 
  which 
  he 
  

   named 
  Distoma 
  renale.- 
  This 
  also 
  occurred 
  in 
  the 
  kidney, 
  and 
  was 
  

   not 
  encysted 
  ; 
  but 
  it 
  was 
  quite 
  twice 
  the 
  size 
  of 
  the 
  form 
  found 
  in 
  

   Hygromia 
  limhata, 
  and 
  the 
  younger 
  examples 
  had 
  short 
  tails. 
  

   Nevertheless, 
  Miss 
  M. 
  V. 
  Lebour, 
  who 
  has 
  very 
  kindly 
  examined 
  the 
  

   specimens 
  that 
  the 
  writer 
  found 
  and 
  mounted, 
  considers 
  that 
  they 
  

   belong 
  to 
  a 
  form 
  which 
  is 
  probably 
  allied 
  to 
  Filippi's 
  species, 
  but 
  

   may 
  prove 
  to 
  be 
  new 
  to 
  science. 
  

  

  Central 
  Nehvous 
  System. 
  (PL 
  II, 
  fig. 
  1.) 
  — 
  The 
  cerebral 
  ganglia 
  

   were 
  situated 
  above 
  the 
  anterior 
  end 
  of 
  the 
  buccal 
  mass 
  in 
  the 
  

   specimens 
  examined, 
  and 
  showed 
  distinct 
  anterior 
  and 
  lateral 
  lobes. 
  

   The 
  length 
  of 
  the 
  cerebral 
  commissure 
  is 
  about 
  equal 
  to 
  the 
  breadth 
  

   of 
  each 
  ganglion. 
  The 
  small 
  buccal 
  ganglia 
  are 
  transversely 
  elongated, 
  

   and 
  occupy 
  their 
  usual 
  position 
  just 
  behind 
  the 
  opening 
  of 
  the 
  

   oesophagus. 
  

  

  The 
  remaining 
  ganglia 
  form 
  a 
  compact 
  group 
  beneath 
  the 
  buccal 
  

   mass. 
  The 
  pedal 
  ganglia 
  are 
  rather 
  broad, 
  and 
  each 
  bears 
  a 
  con- 
  

   spicuous 
  otocyst 
  towards 
  the 
  posterior 
  edge 
  of 
  its 
  lower 
  surface. 
  The 
  

   visceral 
  ganglia 
  show 
  a 
  considerable 
  amount 
  of 
  concentration, 
  for 
  not 
  

   only 
  is 
  the 
  left 
  parietal 
  ganglion 
  fused 
  with 
  the 
  abdominal 
  ganglion, 
  

   as 
  is 
  usual 
  in 
  the 
  Helicidae, 
  but 
  the 
  right 
  parietal 
  ganglion 
  is 
  ])ractically 
  

   united 
  with 
  the 
  right 
  pleural 
  ganglion, 
  as 
  will 
  be 
  seen 
  from 
  the 
  

   figure. 
  

  

  DroESXivE 
  System. 
  — 
  The 
  jaw 
  (pi. 
  Ill, 
  fig. 
  27) 
  is 
  rather 
  thin, 
  

   light 
  brown, 
  and 
  about 
  1-4 
  mm. 
  in 
  length. 
  It 
  is 
  crescentic 
  in 
  form, 
  

   but 
  slightly 
  broader 
  than 
  usual. 
  It 
  is 
  crossed 
  by 
  between 
  thirty 
  and 
  

   thirty-five 
  low 
  and 
  rather 
  inconspicuous 
  ridges 
  or 
  folds, 
  which, 
  how- 
  

   ever, 
  are 
  slightly 
  more 
  prominent 
  towards 
  the 
  ends 
  of 
  the 
  jaw 
  than 
  in 
  

  

  ^ 
  " 
  Mikrographie 
  einiger 
  Drusenapparate 
  der 
  niederen 
  Thiere 
  " 
  : 
  Archiv 
  fiir 
  

  

  Anat. 
  Phys. 
  u. 
  Wiss. 
  Medecin, 
  1846, 
  p. 
  5, 
  pi. 
  i, 
  fig. 
  2. 
  

   - 
  " 
  Deuxieme 
  Memoire 
  pour 
  servir 
  a 
  I'Histoire 
  Gen^tique 
  des 
  Trematodes 
  " 
  : 
  

  

  Mem. 
  della 
  Keale 
  Accademia 
  delle 
  Scienze 
  di 
  Torino, 
  ser. 
  II, 
  vol. 
  xvi, 
  

  

  1857, 
  p. 
  435, 
  pi. 
  ii, 
  fig. 
  21. 
  

  

  