﻿boycott: 
  sexual 
  characters 
  in 
  PO.VATIAS 
  ELEGAXS. 
  

  

  129 
  

  

  (35 
  per 
  cent) 
  are 
  larger 
  than 
  the 
  largest 
  male, 
  the 
  average 
  female 
  

   being 
  1*2 
  mm. 
  longer 
  and 
  0-8 
  mm. 
  wider 
  than 
  the 
  average 
  male. 
  If 
  

   anyone 
  therefore 
  wants 
  to 
  breed 
  Pomatias 
  it 
  is 
  probably 
  safe 
  to 
  

   assume 
  that 
  the 
  largest 
  shells 
  are 
  females 
  and 
  the 
  smallest 
  males 
  ; 
  

   about 
  two-thirds 
  mi<;ht 
  from 
  their 
  size 
  be 
  of 
  either 
  sex. 
  

  

  It 
  would 
  be 
  a 
  matter 
  of 
  mucli 
  interest 
  to 
  determine 
  whether 
  there 
  

   is 
  any 
  size 
  selection 
  in 
  mating. 
  In 
  the 
  present 
  series 
  only 
  six 
  pairs 
  

   in 
  each 
  case 
  the 
  male 
  was 
  smaller 
  than 
  the- 
  

  

  II. 
  ToMiDiTr 
  OF 
  Shell. 
  

   Taking 
  next 
  the 
  question 
  whether 
  the 
  tumidity 
  ( 
  

  

  altitude 
  

  

  , 
  ,- 
  ^ 
  index) 
  

   xliameter 
  ' 
  

  

  differs 
  in 
  the 
  two 
  sexes, 
  we 
  have 
  the 
  following 
  figui'es, 
  the 
  shells 
  

  

  being 
  grouped 
  by 
  altitude 
  into 
  half-millimetre 
  groups 
  : 
  — 
  

  

  Taking 
  the 
  results 
  as 
  a 
  whole, 
  or 
  dealing 
  only 
  with 
  the 
  groups 
  

   (13"5 
  and 
  14*0 
  mm. 
  altitude) 
  which 
  contain 
  a 
  fair 
  number 
  of 
  both 
  

   males 
  and 
  females 
  not 
  differing 
  very 
  grossly 
  in 
  size, 
  there 
  is 
  no 
  

   evidence 
  that 
  there 
  is 
  any 
  sexual 
  difference 
  in 
  tumidity. 
  The 
  index 
  

   has 
  a 
  low 
  variability,^ 
  and 
  the 
  evidence 
  that 
  it 
  varies 
  with 
  size 
  is 
  

   indefinite, 
  though 
  there 
  is 
  some 
  suggestion 
  that 
  the 
  larger 
  shells 
  are 
  

   relatively 
  more 
  slender. 
  

  

  Corresponding 
  with 
  a 
  high 
  correlation 
  ( 
  + 
  0-92) 
  between 
  altitude 
  and 
  diameter. 
  

  

  