﻿2 
  Dr. 
  H. 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  

  

  elation 
  with 
  flowers 
  ? 
  So 
  far 
  as 
  butterflies 
  are 
  concerned, 
  

   colour 
  would 
  seem 
  to 
  be 
  inseparably 
  associated 
  with 
  their 
  

   very 
  existence, 
  and 
  to 
  be 
  told, 
  with 
  an 
  alleged 
  weight 
  of 
  

   evidence, 
  that 
  their 
  own 
  colours 
  and 
  those 
  of 
  their 
  sur- 
  

   roundings 
  have 
  for 
  them 
  no 
  existence, 
  is 
  to 
  receive 
  a 
  rude 
  

   shock 
  to 
  our 
  most 
  cherished 
  traditions, 
  however 
  clearly 
  we 
  

   may 
  reaUse 
  the 
  obvious 
  fact 
  that 
  the 
  existence 
  of 
  colours 
  

   is 
  no 
  proof 
  that 
  they 
  were 
  intended 
  to 
  be 
  seen. 
  

  

  My 
  original 
  intention 
  then 
  was 
  to 
  try 
  to 
  carry 
  out 
  a 
  

   series 
  of 
  experiments 
  on 
  the 
  question 
  of 
  colour 
  vision 
  only, 
  

   but 
  closer 
  acquaintance 
  with 
  existing 
  works 
  on 
  insect 
  

   vision 
  convinced 
  me 
  that 
  there 
  was 
  scope 
  for 
  a 
  somewhat 
  

   wider 
  examination 
  of 
  the 
  subject, 
  in 
  spite 
  of 
  the 
  fact 
  that, 
  

   given 
  the 
  power 
  of 
  sight, 
  by 
  whatever 
  means 
  this 
  power 
  

   may 
  be 
  exercised, 
  the 
  histological 
  structure 
  of 
  the 
  crea- 
  

   ture's 
  eyes 
  is 
  but 
  little 
  likely 
  to 
  demonstrate 
  or 
  disprove 
  

   the 
  power 
  to 
  distinguish 
  colours. 
  

  

  The 
  present 
  paper 
  resolves 
  itself, 
  therefore, 
  into 
  two 
  

   parts, 
  the 
  nature 
  and 
  position 
  of 
  the 
  image 
  in 
  the 
  eye, 
  

   together 
  with 
  the 
  character 
  of 
  the 
  supposed 
  organs 
  of 
  

   perception, 
  and 
  secondly, 
  the 
  evidence 
  for 
  and 
  against 
  a 
  

   capacity 
  for 
  distinguishing 
  those 
  differences 
  in 
  the 
  wave- 
  

   lengths 
  of 
  hght 
  which 
  we 
  ourselves 
  speak 
  of 
  as 
  colours. 
  

  

  Rather 
  for 
  the 
  latter 
  purpose 
  than 
  the 
  former 
  I 
  have 
  

   chosen 
  as 
  a 
  type 
  the 
  insects 
  referred 
  to 
  in 
  the 
  title, 
  since 
  

   the 
  question. 
  Do 
  insects 
  distinguish 
  colours 
  ? 
  is 
  about 
  as 
  

   vague 
  as 
  an 
  inquiry 
  as 
  to 
  whether 
  birds 
  are 
  black. 
  There 
  

   are 
  many 
  species 
  of 
  insects 
  which 
  can 
  have 
  no 
  use 
  whatever 
  

   for 
  a 
  sense 
  of 
  colour, 
  apart 
  from 
  the 
  many 
  which 
  we 
  know 
  

   to 
  be 
  blind. 
  Nevertheless, 
  in 
  examining 
  the 
  subject 
  of 
  insect 
  

   sight 
  we 
  shall 
  have 
  to 
  refer 
  to 
  insects 
  of 
  other 
  orders 
  and 
  

   even 
  to 
  animals 
  which 
  are 
  not 
  insects 
  at 
  all. 
  

  

  The 
  Structure 
  and 
  Function 
  of 
  Facetted 
  Eyes. 
  

  

  So 
  far 
  as 
  the 
  histological 
  structure 
  of 
  the 
  compound 
  

   eye 
  is 
  concerned, 
  the 
  diSiculties, 
  though 
  considerable, 
  are 
  

   not 
  so 
  great 
  as 
  those 
  which 
  appertain 
  to 
  the 
  nature 
  of 
  

   their 
  function. 
  The 
  extent 
  of 
  our 
  knowledge 
  of 
  the 
  vision 
  

   of 
  any 
  creature 
  will 
  always 
  have 
  certain 
  hmits, 
  though 
  in 
  

   the 
  case 
  of 
  the 
  vertebrate 
  eye 
  we 
  feel 
  able 
  to 
  attain 
  to 
  more 
  

   nearly 
  final 
  conclusions, 
  owing 
  to 
  our 
  personal 
  knowledge 
  

   of 
  our 
  own 
  visual 
  powers 
  and 
  the 
  known 
  homology 
  of 
  

   other 
  vertebrate 
  eyes. 
  Thus 
  we 
  know 
  that 
  in 
  our 
  own 
  

  

  