﻿BOWEIL 
  : 
  ON 
  AN 
  ABNORMAL 
  SPECIMEN 
  OF 
  COCBLICOTA 
  LUBIilCA. 
  313 
  

  

  The 
  body 
  of 
  the 
  snail 
  when 
  extracted 
  from 
  the 
  shell 
  was 
  not 
  found 
  

   to 
  be 
  disproportionately 
  small, 
  as 
  I 
  have 
  previously 
  found 
  in 
  extra 
  

   large 
  specimens 
  of 
  Limncea. 
  The 
  anatomy 
  was 
  examined 
  by 
  serial 
  

   sections 
  ; 
  no 
  gross 
  abnormality 
  was 
  found, 
  and 
  the 
  genitalia 
  have 
  the 
  

   morphology 
  normal 
  to 
  luhrica} 
  The 
  genitalia 
  are, 
  however, 
  small 
  

   (smaller 
  than 
  in 
  normal 
  lubrica) 
  and 
  undeveloped, 
  and 
  the 
  herma- 
  

   phrodite 
  gland 
  is 
  represented 
  by 
  a 
  mass 
  of 
  reticular 
  connective 
  

   tissue 
  without 
  any 
  trace 
  of 
  eggs, 
  or 
  spermatozoa, 
  or 
  of 
  cells 
  which 
  

   might 
  be 
  presumed 
  to 
  be 
  their 
  precursors. 
  

  

  Assuming 
  that 
  the 
  present 
  specimen 
  is 
  in 
  fact 
  C. 
  luhrica, 
  it 
  is 
  

   evident 
  it 
  is 
  monstrously 
  large, 
  the 
  bulk 
  being 
  four 
  or 
  five 
  times 
  

   that 
  of 
  the 
  normal 
  shell. 
  In 
  the 
  absence 
  of 
  definite 
  signs 
  of 
  the 
  

   termination 
  of 
  growth, 
  it 
  is 
  difficult 
  to 
  be 
  quite 
  precise 
  about 
  the 
  

   normal 
  size 
  and 
  variability 
  of 
  luhrica,\)\xt 
  there 
  is 
  a 
  general 
  consensus 
  

   among 
  the 
  authorities 
  who 
  happen 
  to 
  be 
  available 
  tliat 
  the 
  normal 
  

   length 
  is 
  about 
  6 
  ram. 
  

  

  To 
  get 
  some 
  measure 
  of 
  the 
  local 
  size 
  variation, 
  the 
  67 
  largest 
  

   specimens 
  which 
  seemed 
  to 
  be 
  adult 
  out 
  of 
  about 
  150 
  collected 
  from 
  

   the 
  rejectamenta 
  of 
  tlie 
  River 
  Colne 
  were 
  examined; 
  the 
  mean 
  was 
  

   5-7 
  X 
  2-4, 
  '^ 
  maximum 
  65 
  X 
  2-6 
  and 
  6-4 
  X 
  28, 
  minimum 
  5-0 
  X 
  2-3, 
  

   coefficient 
  of 
  variation 
  6'3. 
  Taking 
  the 
  mean 
  length 
  as 
  6 
  mm., 
  if 
  the 
  

   coefficient 
  of 
  variation 
  were 
  as 
  much 
  as 
  10, 
  the 
  greatest 
  normal 
  

   range 
  would 
  be 
  about 
  4 
  to 
  8 
  mm., 
  if 
  it 
  were 
  5 
  (a 
  more 
  likely 
  figure) 
  

   about 
  4"5 
  to 
  7*5 
  mm. 
  In 
  any 
  case 
  it 
  is 
  evident 
  that 
  the 
  present 
  

   specimen 
  is 
  definitely 
  beyond 
  the 
  range 
  of 
  normal 
  variation. 
  

   . 
  What 
  appear 
  to 
  be 
  similar 
  monstrous 
  forms 
  have 
  been 
  noticed 
  

   before. 
  J. 
  W. 
  Taylor 
  describes* 
  under 
  the 
  name 
  Azeca 
  elongata 
  two 
  

   specimens 
  of 
  ^. 
  tridens 
  (?) 
  9 
  X 
  2*5 
  mm. 
  (as 
  against 
  a 
  normal 
  measure- 
  

   ment 
  of 
  about 
  6-25 
  X 
  2'5) 
  with 
  9^ 
  instead 
  of 
  7 
  whorls, 
  one 
  from 
  North 
  

   Wales 
  and 
  one 
  from 
  Yorkshire 
  ; 
  J. 
  W. 
  Jackson 
  has 
  a 
  holocene 
  luh'ica{?) 
  

   10 
  mm. 
  long 
  from 
  the 
  talus 
  of 
  a 
  cave 
  at 
  Clapham 
  in 
  Yorkshire.* 
  It 
  

   is 
  perhaps 
  significant 
  that 
  in 
  each 
  case 
  only 
  a 
  single 
  specimen 
  was 
  

   found 
  and 
  that 
  all 
  these 
  concern 
  allied 
  forms. 
  I 
  know 
  of 
  no 
  obviously 
  

   parallel 
  case 
  among 
  other 
  land 
  raollusca, 
  though 
  Mr. 
  Tomlin 
  suggests 
  

   that 
  the 
  shell 
  he 
  described' 
  as 
  Vertigo 
  heldi 
  was 
  a 
  similarly 
  monstrous 
  

   V. 
  pygmcea. 
  

  

  For 
  the 
  present 
  I 
  prefer 
  to 
  regard 
  my 
  specimen 
  as 
  a 
  form 
  of 
  

   CoMicopa 
  luhrica 
  until 
  more 
  is 
  known 
  as 
  to 
  its 
  nature. 
  It 
  may 
  

   ■well 
  be 
  that 
  these 
  sporadic 
  giants 
  represent 
  an 
  attempt 
  or 
  a 
  tendency 
  

  

  ^ 
  See 
  Sternberg's 
  figure 
  in 
  his 
  Fauna 
  of 
  Denmark 
  : 
  Land 
  Mollusca. 
  

   Ihering's 
  figure 
  reproduced 
  by 
  Taylor 
  {Monograph, 
  vol. 
  i, 
  1900, 
  p. 
  356) 
  

   is 
  incorrect. 
  Moquin-Tandon's 
  figure 
  (Histoire, 
  ii, 
  1855, 
  pi. 
  xxii, 
  fig. 
  17) 
  

   is 
  right, 
  except 
  that 
  he 
  omits 
  the 
  diverticulum 
  on 
  the 
  duct 
  of 
  the 
  

   spermatbeca. 
  

  

  ^ 
  Mean 
  sizes 
  determined 
  from 
  specimens 
  as 
  collected 
  are 
  generally 
  somewhat 
  

   less 
  than 
  those 
  in 
  the 
  textbooks, 
  which 
  are 
  presumably 
  taken 
  from 
  

   picked 
  specimens. 
  

  

  ' 
  Naturalist, 
  1897, 
  p. 
  75. 
  

  

  * 
  Journal 
  of 
  Conchology, 
  vol. 
  xiv, 
  1914, 
  p. 
  238. 
  

  

  ® 
  Journal 
  of 
  Conchology, 
  vol. 
  x, 
  1903, 
  p. 
  307. 
  

  

  