﻿WATSON 
  : 
  NOTES 
  ON 
  TJYOROMIA 
  LIMBATA 
  (dEAP.). 
  127 
  

  

  groove 
  becomes 
  separated 
  from 
  the 
  cavity 
  of 
  the 
  vagina, 
  as 
  will 
  be 
  

   seen 
  from 
  the 
  sections 
  (fig. 
  11). 
  The 
  outer 
  wall 
  of 
  the 
  vagina 
  is 
  

   rather 
  thiu. 
  Its 
  lining 
  is 
  throAvn 
  into 
  longitudinal 
  folds 
  posterior 
  to 
  

   the 
  opening 
  of 
  the 
  dart-sac. 
  Further 
  forwards 
  the 
  muscles 
  of 
  the 
  

   accessorj- 
  sac, 
  etc., 
  converge 
  again 
  to 
  form 
  a 
  large 
  pointed 
  papilla, 
  

   which 
  is 
  contained 
  in 
  the 
  anterior 
  part 
  of 
  tlie 
  vagina 
  and 
  can 
  be 
  

   dimh' 
  seen 
  through 
  its 
  thin 
  walls. 
  This 
  papilla 
  is 
  not 
  solid, 
  but 
  

   contains 
  a 
  narrow 
  central 
  duct, 
  the 
  lumen 
  of 
  wliich 
  is 
  almost 
  in 
  a 
  line 
  

   with 
  that 
  of 
  the 
  dart- 
  sac. 
  

  

  The 
  vas 
  deferens 
  is 
  slender 
  and 
  of 
  considerable 
  length, 
  passing 
  

   forwards 
  near 
  the 
  vagina, 
  and 
  then 
  curving 
  I'ouiid 
  beneath 
  the 
  

   retractor 
  of 
  the 
  right 
  upper 
  tentacle, 
  and 
  extending 
  a 
  loiig 
  way 
  back 
  

   to 
  unite 
  with 
  the 
  posterior 
  end 
  of 
  the 
  epiphallus 
  at 
  the 
  base 
  of 
  the 
  

   flagellura. 
  The 
  latter 
  organ 
  is 
  very 
  small, 
  but 
  the 
  epiphallus 
  is 
  

   remarkably 
  long, 
  attaining 
  a 
  length 
  of 
  18 
  or 
  20 
  mm. 
  Its 
  walls 
  are 
  

   longitudinally 
  folded 
  within. 
  The 
  penis 
  scarcely 
  exceeds 
  3 
  mm. 
  in 
  

   length 
  ; 
  it 
  is 
  a 
  little 
  broader 
  than 
  the 
  epiphallus, 
  from 
  which 
  it 
  is 
  

   marked 
  off 
  externally 
  by 
  a 
  slight 
  transverse 
  groove. 
  It 
  contains 
  

   a 
  large 
  cylindrical 
  penial 
  papilla, 
  obtusely 
  pointed 
  in 
  front, 
  with 
  

   a 
  crescentic 
  terminal 
  opening. 
  The 
  genital 
  atrium 
  is 
  rather 
  short. 
  

   As 
  already 
  mentioned, 
  the 
  anterior 
  part 
  of 
  the 
  epiphallus 
  is 
  attached 
  

   to 
  the 
  genital 
  atrium 
  by 
  a 
  series 
  of 
  slender 
  muscles, 
  and 
  just 
  posterior 
  

   to 
  these 
  the 
  penial 
  retractor 
  is 
  inserted. 
  

  

  The 
  spermatozoa 
  (pi. 
  II, 
  fig. 
  8) 
  when 
  mature 
  liave 
  narrow 
  lieads 
  

   pointed 
  in 
  front, 
  and 
  extremely 
  long 
  slender 
  tails. 
  The 
  usual 
  spiral 
  

   structure 
  of 
  the 
  anterior 
  part 
  of 
  the 
  tail 
  can 
  scarcely 
  be 
  discerned 
  

   even 
  under 
  a 
  rV 
  in- 
  oil-immersion 
  objective. 
  In 
  the 
  immature 
  

   spermatazoon 
  the 
  head 
  is 
  broader, 
  and 
  the 
  tail 
  follows 
  a 
  zigzag 
  or 
  

   irregularly 
  spiral 
  course 
  within 
  the 
  residual 
  protoplasm. 
  

  

  This 
  species 
  forms 
  a 
  remarkable 
  spermatophore 
  of 
  a 
  brownish 
  

   colour 
  and 
  nearly 
  20 
  mm. 
  in 
  length 
  (pi. 
  Ill, 
  fig. 
  20). 
  The 
  ])osterior 
  

   part 
  is 
  cylindrical, 
  and 
  the 
  extremity 
  is 
  pointed 
  and 
  abruptly 
  curved 
  

   downwards, 
  being 
  probably 
  secreted 
  in 
  the 
  small 
  flagellum. 
  About 
  

   the 
  middle 
  of 
  its 
  length, 
  however, 
  the 
  top 
  splits 
  open, 
  so 
  that 
  the 
  

   anterior 
  part 
  is 
  trough-shaped. 
  Externally 
  the 
  spermatophore 
  is 
  

   furnished 
  with 
  between 
  ten 
  and 
  fifteen 
  longitudinal 
  ridges, 
  and, 
  with 
  

   the 
  exception 
  of 
  one 
  or 
  two 
  on 
  the 
  top, 
  these 
  ridges 
  are 
  serrated. 
  

   The 
  teeth 
  on 
  the 
  ridges 
  are 
  most 
  prominent 
  towards 
  the 
  posterior 
  

   end 
  of 
  the 
  spermatophore, 
  and 
  although 
  they 
  are 
  rather 
  irregular 
  in 
  

   form, 
  their 
  points 
  are 
  always 
  directed 
  backwards, 
  their 
  function 
  

   doubtless 
  being 
  to 
  facilitate 
  the 
  forward 
  movement 
  of 
  the 
  spermato- 
  

   phore. 
  When 
  transferred 
  to 
  another 
  snail 
  this 
  structure 
  occupies 
  

   the 
  entire 
  length 
  of 
  the 
  unusually 
  elongated 
  spermatheca. 
  Indeed, 
  

   tliere 
  can 
  be 
  little 
  doubt 
  that 
  the 
  peculiar 
  form 
  of 
  spermatheca 
  that 
  

   we 
  find 
  in 
  this 
  species 
  has 
  been 
  evolved 
  in 
  order 
  to 
  accommodate 
  the 
  

   very 
  long 
  spermatophore, 
  just 
  as 
  the 
  size 
  of 
  this 
  structure 
  is 
  to 
  be 
  

   correlated 
  with 
  the 
  unusual 
  development 
  of 
  the 
  epiphallus 
  in 
  which 
  

   it 
  is 
  secreted. 
  

  

  According 
  to 
  Moquin-Tandon 
  ^ 
  the 
  eggs 
  of 
  Hygromia 
  Umhata 
  

  

  ' 
  Hist. 
  Nat. 
  Moll. 
  terr. 
  et 
  fluv. 
  de 
  France, 
  vol. 
  ii, 
  1856, 
  p. 
  19G. 
  

   VOL. 
  XIII. 
  — 
  OCTOBEK, 
  1919. 
  10 
  

  

  