﻿HISTOLOGY 
  OF 
  THE 
  LOCUST 
  AND 
  CRICKET. 
  187 
  

  

  they 
  always 
  run 
  nearly 
  perpendicular 
  to 
  the 
  surface 
  to 
  the 
  cuticula. 
  

   Directly 
  over 
  each 
  pore 
  there 
  sits 
  a 
  stiff 
  chitiuous 
  tapering 
  hair 
  (Fig. 
  4 
  h 
  

   and 
  h 
  1 
  ), 
  which 
  is 
  generally 
  slightly 
  curved. 
  This 
  relation 
  of 
  the 
  hairs 
  

   and 
  pores 
  has 
  also 
  been 
  described 
  by 
  Leydig, 
  227 
  and 
  is 
  well 
  known 
  to 
  

   naturalists. 
  The 
  hairs 
  are 
  all 
  small, 
  though 
  very 
  unequal 
  in 
  size, 
  the 
  

   difference 
  in 
  the 
  extremes 
  being 
  much 
  greater 
  than 
  between 
  h 
  and 
  h 
  l 
  in 
  

   Fig. 
  4. 
  The 
  hairs 
  do 
  not 
  stand 
  upright, 
  but 
  are 
  so 
  inclined 
  as 
  to 
  point 
  

   towards 
  the 
  posterior 
  end 
  of 
  the 
  body. 
  

  

  Each 
  hair 
  is 
  constricted 
  around 
  its 
  base 
  (Fig. 
  63 
  h), 
  forming 
  a 
  narrow 
  

   neck, 
  below 
  which 
  it 
  expands 
  again, 
  spreading 
  out 
  to 
  make 
  the 
  circular 
  

   covering 
  membrane 
  of 
  the 
  hair 
  pore. 
  This 
  membrane 
  is 
  very 
  thin, 
  but 
  

   has 
  a 
  thickened 
  rim. 
  In 
  consequence 
  of 
  this 
  constriction 
  these 
  hairs 
  

   are 
  commonly 
  said 
  to 
  be 
  articulated. 
  They 
  are 
  not 
  homogeneous, 
  

   but 
  have 
  a 
  distinct 
  medulla 
  (Fig. 
  63 
  A), 
  which 
  is 
  probably 
  a 
  prolonga- 
  

   tion 
  of 
  the 
  cell 
  which 
  forms 
  the 
  hair. 
  These 
  cells 
  have 
  been 
  described 
  

   by 
  Graber. 
  228 
  They 
  were 
  formerly 
  called 
  u 
  Hautdrusen" 
  by 
  Leydig 
  and 
  

   others. 
  They 
  are, 
  as 
  it 
  were, 
  suspended 
  from 
  the 
  inner 
  side 
  of 
  the 
  large 
  

   pores 
  as 
  the 
  hairs 
  are 
  from 
  the 
  outer. 
  They 
  are 
  somewhat 
  pear-shaped, 
  

   and 
  four 
  or 
  five 
  times 
  the 
  diameter 
  of 
  the 
  ordinary 
  epidermal 
  cells, 
  and 
  

   have 
  correspondingly 
  large 
  round 
  nuclei 
  ; 
  their 
  contents 
  are 
  very 
  gran- 
  

   ular. 
  There 
  are 
  usually 
  two 
  or 
  three, 
  rarely 
  but 
  one 
  nucleus 
  in 
  each 
  

   hair-cell. 
  Graber 
  suggests 
  the 
  name 
  of 
  trichogens 
  for 
  these 
  cells. 
  They 
  

   are 
  probably 
  strictly 
  homogeneous 
  with 
  the 
  scale-cells 
  of 
  the 
  Lepidop- 
  

   tera 
  ; 
  the 
  cells 
  differ 
  in 
  the 
  two 
  orders 
  of 
  insects 
  in 
  that 
  they 
  bear 
  a 
  

   round 
  hair 
  in 
  one 
  case, 
  a 
  flattened 
  hair 
  in 
  the 
  other. 
  The 
  plausibility 
  

   of 
  this 
  suggestion 
  must, 
  I 
  think, 
  strike 
  every 
  one 
  who 
  is 
  acquainted 
  

   with 
  the 
  account 
  of 
  the 
  structure 
  and 
  development 
  of 
  the 
  scales 
  in 
  but- 
  

   terflies 
  given 
  by 
  Semper. 
  229 
  If 
  the 
  homology 
  is 
  correct, 
  these 
  hair 
  or 
  scale 
  

   cells 
  must 
  be 
  regarded 
  as 
  specially 
  characteristic 
  of 
  insects, 
  or, 
  possibly, 
  

   of 
  arthropods 
  generally. 
  

  

  The 
  articular 
  membrane, 
  though 
  a 
  part 
  of 
  the 
  cuticula, 
  has 
  either 
  no, 
  or 
  

   at 
  most 
  very 
  few, 
  hairs. 
  In 
  the 
  locusts 
  the 
  cuticula 
  at 
  the 
  joint 
  is 
  much 
  

   thicker 
  and 
  paler 
  in 
  color 
  than 
  elsewhere 
  (Fig. 
  5, 
  art.), 
  being 
  not 
  only 
  

   thrown 
  up 
  into 
  folds, 
  but 
  also 
  covered 
  with 
  numerous 
  minute 
  pyramidal 
  

   spines. 
  In 
  the 
  locust 
  the 
  first 
  abdominal 
  segment 
  lacks 
  an 
  independent 
  

   articular 
  membrane, 
  its 
  own 
  entering 
  into 
  the 
  formation 
  of 
  the 
  sterno- 
  

   coxal 
  membrane, 
  or 
  articular 
  capsule 
  of 
  the 
  third 
  or 
  metathoracic 
  limb. 
  

   On 
  the 
  sides 
  of 
  the 
  segment 
  a 
  kidney 
  -shaped 
  piece 
  of 
  the 
  cuticula 
  un- 
  

   dergoes 
  peculiar 
  modifications 
  to 
  enter 
  into 
  the 
  formation 
  of 
  the 
  tym- 
  

   panal 
  apparatus. 
  

  

  In 
  Anabrus 
  the 
  cuticula 
  presents 
  the 
  following 
  characteristics, 
  besides 
  

   those 
  which 
  have 
  been 
  mentioned 
  as 
  found 
  in 
  both 
  it 
  and 
  the 
  locusts: 
  

  

  First, 
  there 
  are 
  projecting 
  conical 
  nodules 
  scattered 
  irregularly 
  over 
  

   it, 
  as 
  cau 
  be 
  seen 
  in 
  a 
  surface 
  view. 
  (Fig. 
  59, 
  b 
  b.) 
  These 
  cones 
  are 
  less 
  

  

  ^Leydig: 
  Lehrbuch 
  der 
  Histologie, 
  1857, 
  p. 
  Ill, 
  Fig. 
  56. 
  

   2=8 
  Graber: 
  Denk. 
  Wien. 
  Akad., 
  xxxvi, 
  p. 
  35 
  (1876). 
  

   229 
  Semper 
  : 
  Zeit. 
  fur 
  wiss. 
  Zool. 
  Bd. 
  viii, 
  p. 
  328. 
  

  

  