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  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  each 
  disk 
  being 
  folded 
  together 
  and 
  bent 
  downwards 
  before 
  and 
  behind, 
  its 
  border 
  

   being 
  thickened 
  and 
  the 
  inner 
  portion 
  radiated. 
  By 
  very 
  careful 
  dissection 
  he 
  found 
  

   these 
  bodies 
  to 
  be 
  connected 
  on 
  each 
  side 
  with 
  a 
  short 
  pedicle, 
  which 
  bifurcates 
  below 
  

   to 
  end 
  in 
  two 
  tubercles. 
  One 
  of 
  these 
  tubercles 
  is 
  directed 
  towards 
  the 
  middle 
  line, 
  

   and 
  approaches 
  but 
  does 
  not 
  touch 
  the 
  corresponding 
  process 
  of 
  the 
  opj)osite 
  side. 
  

   The 
  second 
  tubercle 
  is 
  directed 
  forwards, 
  and 
  is 
  in 
  close 
  relation 
  to 
  the 
  front 
  wall 
  of 
  

   the 
  head, 
  being 
  only 
  covered 
  by 
  the 
  pia 
  mater 
  [neurilemma]. 
  These 
  convoluted 
  

   bodies 
  and 
  the 
  stalks 
  upon 
  which 
  they 
  are 
  mounted 
  are 
  compared 
  by 
  Dajardin 
  to 
  cer- 
  

   tain 
  kinds 
  of 
  mushrooms, 
  and 
  this 
  idea 
  has 
  been 
  retained 
  by 
  more 
  recent 
  writers 
  on 
  

   the 
  subject. 
  

  

  The 
  form 
  of 
  the 
  mushroom 
  body 
  is 
  much 
  more 
  complicated 
  in 
  the 
  

   bee 
  or 
  ant 
  than 
  in 
  insects 
  of 
  other 
  orders. 
  In 
  the 
  cockroach 
  and 
  in 
  other 
  

   Orthoptera, 
  notably 
  the 
  locust, 
  the 
  four 
  divisions 
  of 
  the 
  calices 
  are 
  united 
  

   into 
  two 
  $ 
  while 
  the 
  structure 
  of 
  the 
  calyx 
  in 
  the 
  cockroach 
  is 
  quite 
  

   different 
  from 
  that 
  of 
  the 
  locust. 
  Mr. 
  Newton, 
  in 
  his 
  description, 
  not- 
  

   withstanding 
  Dujardin's 
  statement, 
  appears 
  to 
  practically 
  limit 
  the 
  term 
  

   " 
  mushroom 
  body 
  " 
  to 
  the 
  cap 
  or 
  calyx 
  on 
  the 
  end 
  of 
  the 
  stalk. 
  In 
  the 
  

   following 
  description 
  we 
  apply 
  the 
  term 
  "mushroom 
  body" 
  to 
  the 
  en- 
  

   tire 
  structure, 
  including 
  the 
  base 
  or 
  trabecula, 
  the 
  double 
  stalk, 
  and 
  the 
  

   cap 
  or 
  calyx. 
  

  

  So 
  far 
  as 
  we 
  have 
  been 
  able 
  to 
  observe, 
  the 
  double 
  stalk 
  of 
  the 
  mush- 
  

   room 
  body 
  rests 
  on 
  a 
  rounded 
  mass 
  of 
  granulo-fibrous 
  nerve 
  matter; 
  this 
  

   rounded 
  mass 
  or 
  base 
  of 
  the 
  column 
  is 
  called 
  the 
  trabecula 
  (PL 
  X, 
  Fig. 
  

   2, 
  trab.). 
  The 
  two 
  trabecule 
  (one 
  in 
  each 
  hemisphere) 
  are 
  much 
  more 
  

   widely 
  separated 
  (in 
  my 
  sections) 
  than 
  in 
  the 
  cockroach 
  or 
  in 
  those 
  

   insects 
  studied 
  by 
  Flogel 
  ,• 
  the 
  space 
  between 
  them 
  beiug 
  filled 
  by 
  sl 
  

   loose 
  cellular 
  mass 
  containing 
  small 
  nucleated 
  cells. 
  The 
  thickness 
  of 
  

   each 
  trabecula 
  is 
  greater 
  than 
  that 
  of 
  the 
  double 
  stalk. 
  Section 
  14 
  

   passes 
  through 
  the 
  outer 
  or 
  anterior 
  edge 
  of 
  the 
  trabecula, 
  and 
  also 
  

   through 
  the 
  calices 
  at 
  some 
  distance 
  from 
  the 
  edge. 
  Section 
  18 
  (Fig. 
  4) 
  

   does 
  not 
  include 
  it, 
  though 
  showing 
  well 
  the 
  mushroom 
  body, 
  with 
  the 
  

   exception 
  of 
  the 
  base 
  of 
  the 
  double 
  stalk. 
  It 
  follows 
  that 
  the 
  thickness 
  

   of 
  the 
  trabecula 
  is 
  about 
  3 
  -§-o 
  of 
  an 
  inch. 
  

  

  The 
  substance 
  of 
  the 
  trabecula 
  is 
  seen 
  to 
  be 
  minutely 
  fibrous 
  under 
  a 
  

   power 
  of 
  725 
  diameters, 
  with 
  masses 
  of 
  granules 
  among 
  the 
  fibers 
  which 
  

   are 
  much 
  finer 
  than 
  in 
  the 
  optic 
  or 
  antennal 
  lobes. 
  At 
  the 
  point 
  passed 
  

   through 
  by 
  section 
  17 
  the 
  trabecular 
  appear 
  to 
  have 
  no 
  connection 
  with 
  

   the 
  stalk, 
  but 
  the 
  latter 
  appear 
  to 
  stop 
  abruptly 
  just 
  before 
  reaching 
  it, 
  

   the 
  envelope 
  of 
  ganglionic 
  cells 
  and 
  fibers 
  surrounding 
  the 
  trabecule 
  

   being 
  interposed 
  between 
  the 
  base 
  of 
  the 
  stalk 
  and 
  the 
  trabecula. 
  (This 
  

   does 
  not 
  preclude 
  the 
  fact 
  that 
  the 
  stalk 
  does 
  not 
  arise 
  from 
  the 
  trabe- 
  

   cula, 
  though 
  there 
  are 
  no 
  signs 
  of 
  it 
  in 
  this 
  section 
  j 
  for 
  it 
  clearly 
  ap- 
  

   pears 
  to 
  thus 
  arise 
  in 
  the 
  drawings 
  and 
  descriptions 
  of 
  Dietl, 
  Flogel, 
  

   and 
  Newton 
  ). 
  

  

  The 
  structure 
  of 
  the 
  trabecular 
  in 
  the 
  locust, 
  judging 
  from 
  our 
  sections, 
  

   appears 
  to 
  be 
  more 
  complex 
  than 
  would 
  be 
  inferred 
  from 
  the 
  observa- 
  

   tions 
  of 
  the 
  other 
  observers 
  just 
  mentioned. 
  Section 
  17 
  (PI. 
  X, 
  Fig. 
  2, 
  

   trab.) 
  passes 
  through 
  the 
  middle 
  of 
  each 
  of 
  these 
  bodies, 
  and 
  it 
  then 
  ap- 
  

  

  