﻿Explanation 
  of 
  Plate 
  I. 
  

  

  Section 
  through 
  an 
  eye 
  of 
  V. 
  urticae 
  in 
  the 
  plane 
  of 
  the 
  expanded 
  

   wings 
  X 
  60. 
  

  

  A. 
  The 
  corneal 
  layer 
  showing 
  the 
  lenses. 
  

  

  B. 
  The 
  processus 
  corneae. 
  

  

  G. 
  The 
  layer 
  of 
  the 
  "crystalline 
  cones." 
  

  

  D. 
  The 
  ommatidia, 
  each 
  of 
  which 
  consists 
  of 
  eight 
  elongated 
  

  

  nerve 
  end 
  cells, 
  the 
  transparent 
  inner 
  longitudinal 
  margins 
  

   of 
  which 
  form 
  the 
  rhabdom. 
  

  

  E. 
  The 
  basal, 
  or 
  fenestrated 
  membrane. 
  

  

  F. 
  The 
  nerve 
  bundles 
  leading 
  from 
  the 
  ommatidia 
  to 
  the 
  peri- 
  

  

  opticon. 
  

   O. 
  The 
  periopticon. 
  

   H. 
  The 
  epiopticon. 
  

  

  In 
  the 
  neighbourhood 
  of 
  the 
  cones 
  is 
  seen 
  a 
  layer 
  of 
  pigment 
  

   granules, 
  the 
  contents 
  of 
  the 
  pigment 
  cells 
  there 
  situated. 
  A 
  

   second 
  less 
  dense 
  pigmentation 
  occurs 
  at 
  the 
  basal 
  membrane. 
  

   Just 
  beneath 
  the 
  latter 
  is 
  a 
  layer 
  of 
  heavily 
  nucleated 
  cells 
  of 
  which 
  

   there 
  is 
  one 
  to 
  each 
  ommatidium. 
  The 
  blank 
  areas 
  between 
  the 
  

   nerve 
  bundles 
  are 
  tracheal 
  spaces. 
  

  

  