﻿384 
  Dr. 
  F. 
  A. 
  Dixey 
  on 
  

  

  of 
  the 
  lamina. 
  If 
  the 
  scale 
  be 
  stained 
  with 
  a 
  solution 
  of 
  

   coal-tar 
  " 
  light 
  green 
  " 
  in 
  alcohol 
  and 
  examined 
  dry, 
  the 
  

   varicose 
  ribs 
  are 
  shown 
  with 
  greater 
  distinctness, 
  and 
  the 
  

   central 
  area 
  is 
  seen 
  to 
  contain 
  a 
  homogeneous 
  body 
  stain- 
  

   ing 
  deeply 
  with 
  the 
  reagent; 
  this 
  body, 
  hereinafter 
  re- 
  

   ferred 
  to 
  as 
  the 
  " 
  central 
  substance," 
  corresponds 
  with 
  the 
  

   highly-refracting 
  patch 
  visible 
  in 
  the 
  unstained 
  scale. 
  

   The 
  granules 
  of 
  the 
  central 
  area 
  appear 
  to 
  be 
  unstained; 
  

   but 
  the 
  presence 
  of 
  the 
  granules, 
  and 
  especially 
  the 
  deep 
  

   coloration 
  of 
  the 
  central 
  substance, 
  interferes 
  with 
  the 
  

   tracing 
  of 
  the 
  ribs 
  in 
  their 
  course 
  through 
  the 
  central 
  area. 
  

   If 
  the 
  stained 
  scale 
  be 
  mounted 
  in 
  Canada 
  balsam, 
  it 
  

   becomes 
  so 
  transparent 
  that 
  over 
  the 
  greater 
  part 
  of 
  the 
  

   lamina 
  the 
  ribbing 
  can 
  only 
  be 
  made 
  out 
  with 
  difficulty. 
  

   The 
  central 
  substance, 
  however, 
  is 
  very 
  clearly 
  defined; 
  

   and 
  in 
  its 
  neighbourhood 
  the 
  ribbing 
  and 
  granules 
  are 
  

   fairly 
  distinct. 
  

  

  Further 
  fight 
  upon 
  the 
  relation 
  of 
  the 
  central 
  substance 
  

   to 
  the 
  general 
  structure 
  of 
  the 
  scale 
  is 
  afforded 
  by 
  some 
  

   sections 
  prepared 
  with 
  great 
  skill 
  by 
  my 
  friend 
  Dr. 
  H. 
  

   Eltringham. 
  Sections 
  taken 
  longitudinally 
  through 
  the 
  

   fore-wing 
  in 
  a 
  male 
  specimen 
  of 
  P. 
  liliana, 
  stained 
  with 
  

   light 
  green 
  and 
  safranin 
  and 
  mounted 
  in 
  Canada 
  balsam, 
  

   show 
  the 
  wing-membrane 
  stained 
  a 
  deep 
  pink, 
  with 
  sockets 
  

   on 
  both 
  upper 
  and 
  lower 
  surface 
  for 
  the 
  reception 
  of 
  the 
  

   footstalks 
  of 
  the 
  scales 
  (PI. 
  XVI, 
  fig. 
  2). 
  Sockets 
  of 
  the 
  

   ordinary 
  character 
  occur 
  on 
  both 
  surfaces; 
  but 
  on 
  the 
  

   upper 
  surface, 
  in 
  addition 
  to 
  these, 
  there 
  are 
  visible 
  the 
  

   special 
  sockets 
  for 
  the 
  reception 
  of 
  the 
  basal 
  portion 
  of 
  

   the 
  scent-scales 
  ; 
  further 
  reference 
  to 
  these 
  special 
  sockets 
  

   and 
  the 
  articulating 
  structure 
  of 
  the 
  scale 
  will 
  be 
  made 
  

   later.* 
  Many 
  of 
  the 
  scent-scales 
  are 
  shown 
  in 
  section; 
  

   sometimes 
  the 
  whole 
  length 
  of 
  the 
  scale 
  is 
  visible, 
  from 
  

   the 
  portion 
  engaged 
  in 
  the 
  socket 
  to 
  the 
  tuft 
  of 
  fimbriae 
  

   at 
  the 
  distal 
  extremity 
  (PI. 
  XVI, 
  fig. 
  3). 
  In 
  these 
  cases 
  the 
  

   scale 
  itself 
  exhibits 
  a 
  pink 
  staining, 
  generally 
  paler 
  than 
  

   that 
  of 
  the 
  wing-membrane 
  ; 
  while 
  the 
  central 
  substance 
  (c) 
  

   is 
  distinctly 
  defined 
  and 
  stained 
  blue, 
  this 
  colour 
  being 
  

   apparently 
  the 
  result 
  of 
  the 
  combined 
  action 
  of 
  the 
  two 
  

   staining 
  reagents. 
  The 
  lamina 
  of 
  the 
  scale 
  (d) 
  is 
  for 
  the 
  

   most 
  part 
  extremely 
  thin, 
  but 
  in 
  the 
  region 
  of 
  the 
  central 
  

   substance 
  the 
  upper 
  and 
  lower 
  layers 
  {a 
  and 
  b) 
  separate 
  

  

  * 
  See 
  p. 
  387, 
  ivfra. 
  

  

  