﻿Histology 
  of 
  the 
  Scent-organs 
  in 
  the 
  Genus 
  Hydroptila. 
  427 
  

  

  hairs 
  is 
  as 
  in 
  H. 
  forcipata, 
  but 
  the 
  hairs 
  themselves 
  appear 
  to 
  

   be 
  longitudinallv 
  striated 
  and 
  without 
  the 
  dentate 
  structure 
  

   found 
  in 
  that 
  species. 
  

  

  H. 
  femoralis 
  Eaton. 
  

  

  In 
  this 
  species 
  the 
  lobes, 
  while 
  distinctive 
  in 
  shape, 
  

   resemble 
  somewhat 
  those 
  of 
  H. 
  simulans, 
  their 
  perforate 
  

   portion 
  thickly 
  clothed 
  with 
  cuticle 
  hairs 
  and 
  containing 
  

   a 
  layer 
  of 
  epithelial 
  cells 
  into 
  which 
  the 
  stalks 
  of 
  these 
  

   cuticle 
  hairs 
  project. 
  Attached 
  to 
  the 
  inner 
  face 
  of 
  the 
  

   lobe 
  there 
  are 
  numerous 
  heavily 
  ribbed 
  androconia, 
  the 
  

   stalks 
  of 
  which 
  pass 
  through 
  the 
  chitin 
  and 
  communicate 
  

   \vith 
  an 
  epithehal 
  layer 
  beneath. 
  These 
  androconia 
  stain 
  

   very 
  deeply, 
  have 
  an 
  oval 
  section, 
  and 
  a 
  small 
  central 
  

   lumen. 
  The 
  lobes 
  cover 
  two 
  large 
  eversible 
  brushes 
  

   provided 
  with 
  black 
  hairs, 
  the 
  latter 
  being 
  considerably 
  

   expanded 
  at 
  their 
  distal 
  extremities. 
  

  

  The 
  brush 
  bag 
  appears 
  to 
  have 
  much 
  less 
  glandular 
  

   development 
  than 
  in 
  H. 
  simulans. 
  The 
  hairs'are 
  quite 
  char- 
  

   acteristic 
  in 
  structure, 
  being 
  very 
  thick 
  walled 
  and 
  covered 
  

   on 
  the 
  outer 
  surface 
  with 
  whorls 
  of 
  regularly 
  arranged 
  

   projections. 
  Figs. 
  22 
  and 
  24. 
  In 
  many 
  of 
  the 
  transverse 
  

   sections 
  of 
  these 
  hairs 
  there 
  is 
  a 
  sHght 
  staining 
  of 
  the 
  

   central 
  lumen 
  indicating 
  the 
  presence 
  of 
  some 
  structureless 
  

   material 
  in 
  that 
  position, 
  probably 
  a 
  coagulated 
  secretion. 
  

  

  Fio;. 
  25 
  shows 
  a 
  section 
  through 
  the 
  entire 
  head 
  of 
  this 
  

   species. 
  At 
  the 
  lower 
  side 
  of 
  the 
  figure 
  may 
  be 
  seen 
  the 
  

   lobes 
  \vith 
  part 
  of 
  the 
  cellular 
  material 
  they 
  contain, 
  

   and 
  their 
  perforate 
  external 
  surface. 
  Within 
  the 
  inner 
  

   boundary 
  are 
  a 
  few 
  of 
  the 
  androconia 
  cut 
  across 
  and 
  

   portions 
  of 
  the 
  brushes 
  cut 
  obliquely. 
  Fig. 
  21 
  is 
  a 
  view 
  

   of 
  the 
  entire 
  head 
  with 
  brushes 
  partly 
  everted. 
  

  

  H. 
  occulta 
  Eaton, 
  

  

  The 
  organs 
  in 
  this 
  species 
  are 
  more 
  remarkable 
  than 
  in 
  

   any 
  of 
  the 
  others 
  examined. 
  The 
  lobes 
  are 
  narrow 
  and 
  

   somewhat 
  conical. 
  They 
  bear 
  on 
  the 
  inner 
  surface 
  a 
  mem- 
  

   brane, 
  which 
  towards 
  the 
  upper 
  extremity 
  contains 
  a 
  deep 
  

   tubular 
  pocket 
  hned 
  with 
  long 
  androconia. 
  This 
  pocket 
  

   forms 
  in 
  fact 
  a 
  miniature 
  eversible 
  brush 
  bag 
  and 
  can 
  be 
  

   extended 
  so 
  as 
  to 
  form 
  a 
  small 
  secondary 
  brush, 
  the 
  andro- 
  

   conia 
  then 
  radiating 
  from 
  its 
  surface 
  . 
  Besides 
  this 
  structure 
  

   there 
  are 
  a 
  few 
  small 
  androconia 
  near 
  the 
  apex 
  of 
  the 
  inner 
  

  

  