﻿Dr. 
  H. 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  17 
  

  

  in 
  demonstrating 
  the 
  presence 
  of 
  such 
  fibrils, 
  and 
  there 
  is 
  

   in 
  fact 
  no 
  real 
  evidence 
  of 
  their 
  existence. 
  

  

  Jonas 
  (I.e.) 
  describes 
  and 
  figures 
  the 
  structure 
  of 
  many 
  

   Lepidopterous 
  eyes. 
  In 
  his 
  description 
  of 
  the 
  structure 
  

   of 
  the 
  eye 
  he 
  insists 
  on 
  the 
  transversely 
  laminated 
  struc- 
  

   ture 
  of 
  the 
  rhabdom, 
  which 
  he 
  says 
  is 
  quite 
  easy 
  to 
  see. 
  

   The 
  writer 
  cannot 
  agree 
  with 
  this 
  statement. 
  An 
  apparent 
  

   transverse 
  lamination 
  of 
  the 
  rhabdom 
  is 
  occasionally 
  seen 
  

   in 
  osmic 
  acid 
  preparations, 
  but 
  as 
  a 
  rule 
  it 
  is 
  not 
  visible. 
  

   Whether 
  the 
  rhabdom 
  is 
  actually 
  laminated 
  or 
  not, 
  I 
  have 
  

   been 
  unable 
  to 
  decide. 
  Certainly 
  in 
  many 
  cases 
  the 
  fine 
  

   pigment 
  granules 
  when 
  very 
  shghtly 
  out 
  of 
  focus 
  have 
  a 
  

   tendency 
  to 
  suggest 
  transverse 
  fines, 
  and 
  I 
  feel 
  certain 
  

   that 
  in 
  some 
  cases 
  at 
  least 
  this 
  appearance 
  has 
  been 
  thus 
  

   misinterpreted. 
  Jonas 
  failed 
  to 
  discover 
  any 
  nerve 
  fibrillse, 
  

   though 
  in 
  cross 
  sections 
  of 
  the 
  retinulae 
  he 
  saw 
  clear 
  spots 
  

   which 
  he 
  thought 
  might 
  be 
  sections 
  of 
  nerves. 
  He 
  quotes 
  

   Wagner 
  as 
  describing 
  how 
  in 
  Sphinx 
  airopos 
  " 
  the 
  nerve 
  

   threads 
  or 
  visual 
  nerve 
  bundles 
  surround 
  the 
  apex 
  of 
  the 
  

   cone 
  like 
  a 
  calyx, 
  passing 
  thence 
  to 
  its 
  anterior 
  surface, 
  

   and 
  reaching 
  the 
  cornea; 
  the 
  nerve 
  forms 
  a 
  true 
  retina 
  

   which 
  surrounds 
  the 
  cone 
  fike 
  a 
  sheath." 
  Ley 
  dig, 
  as 
  he 
  

   says, 
  took 
  the 
  same 
  view, 
  and 
  he 
  quotes 
  Schultze's 
  minute 
  

   description 
  of 
  the 
  nerve 
  fibrils 
  entering 
  the 
  cone 
  and 
  

   surrounding 
  the 
  apex 
  in 
  a 
  cup-hke 
  fashion. 
  He 
  then 
  

   states 
  :— 
  

  

  " 
  With 
  the 
  help 
  of 
  the 
  apochromatic 
  objective 
  I 
  have 
  

   come 
  to 
  precisely 
  the 
  same 
  results. 
  . 
  . 
  . 
  One 
  almost 
  gains 
  

   the 
  impression 
  that 
  the 
  old 
  authors 
  were 
  right 
  in 
  that 
  

   they 
  maintained 
  that 
  the 
  cone 
  sheath 
  extends 
  as 
  a 
  nerve- 
  

   rod 
  sheath 
  as 
  far 
  as 
  the 
  basal 
  membrane, 
  but 
  a 
  definite 
  

   opinion 
  cannot 
  be 
  formed 
  until 
  entire 
  proof 
  has 
  been 
  

   obtained 
  by 
  the 
  study 
  of 
  development." 
  

  

  It 
  may 
  be 
  noted 
  that 
  these 
  views 
  support 
  those 
  of 
  

   Patten 
  referred 
  to 
  later. 
  

  

  Jonas, 
  though 
  asserting 
  that 
  he 
  has 
  come 
  to 
  the 
  same 
  

   conclusion 
  as 
  Schiiltze 
  in 
  regard 
  to 
  the 
  nerve 
  terminals 
  in 
  

   the 
  compound 
  eye, 
  does 
  not 
  figure 
  them 
  and 
  also 
  states 
  

   that 
  he 
  could 
  not 
  find 
  them. 
  The 
  value 
  of 
  his 
  observa- 
  

   tions 
  is 
  somewhat 
  discounted 
  by 
  a 
  very 
  curious 
  and 
  isolated 
  

   observation. 
  He 
  describes 
  a 
  " 
  cigar-shaped 
  structure 
  " 
  at 
  

   the 
  base 
  of 
  the 
  rhabdom 
  which 
  he 
  appears 
  to 
  have 
  seen 
  

   only 
  in 
  Coenonympha 
  pamphilus. 
  A 
  small 
  text 
  figure 
  

   shows 
  the 
  object 
  as 
  attached 
  to 
  the 
  base 
  of 
  the 
  rhabdom 
  

  

  TRANS. 
  ENT. 
  SOC. 
  LOND. 
  1919. 
  — 
  PARTS 
  I, 
  II. 
  (jULY) 
  C 
  

  

  