﻿THE 
  BRAIN 
  OF 
  THE 
  LOCUST. 
  239 
  

  

  cerebral 
  lobe 
  and 
  the 
  optic 
  ganglion. 
  The 
  oesophagus 
  is 
  situated 
  be- 
  

   neath 
  the 
  cleft 
  under 
  the 
  lower 
  cerebral 
  lobes. 
  The 
  next 
  section 
  (13) 
  

   passes 
  behind 
  the 
  brain, 
  not 
  touching 
  it. 
  These 
  sections 
  are 
  y£o 
  inch 
  

   thick. 
  

  

  Structure 
  of 
  the 
  subcesophageal 
  ganglion 
  (PI. 
  XII, 
  Fig. 
  10). 
  — 
  In 
  its 
  form 
  

   this 
  nerve 
  center 
  is 
  more 
  like 
  the 
  brain 
  than 
  the 
  first 
  thoracic 
  ganglion. 
  

   The 
  figure 
  is 
  drawn 
  from 
  the 
  youngest 
  embryo 
  observed. 
  The 
  ganglion 
  

   seen 
  in 
  section 
  is 
  very 
  much 
  larger 
  and 
  quite 
  different 
  in 
  shape 
  from 
  the 
  

   thoracic 
  ganglia. 
  It 
  expands 
  above 
  the 
  lower 
  fissure 
  between 
  the 
  two 
  

   sides, 
  being 
  very 
  deep 
  and 
  narrow, 
  while 
  the 
  superior 
  furrow 
  is 
  broad 
  

   and 
  shallow. 
  The 
  internal 
  paler 
  portion 
  (when 
  magnified 
  400 
  diam- 
  

   eters) 
  is 
  seen 
  to 
  consist 
  of 
  granules. 
  The 
  stratum 
  of 
  outer 
  cells 
  (the 
  

   future 
  ganglion 
  cells) 
  is 
  thickest 
  on 
  the 
  outside 
  of 
  the 
  upper 
  part 
  of 
  the 
  

   ganglion, 
  and 
  at 
  the 
  base 
  of 
  each 
  hemisphere. 
  

  

  The 
  brain 
  of 
  the 
  freshly-hatched 
  larva 
  of 
  G. 
  spretus. 
  — 
  In 
  the 
  larva 
  but 
  a 
  

   few 
  hours 
  after 
  hatching, 
  the 
  brain, 
  so 
  far 
  as 
  I 
  can 
  learn 
  from 
  four 
  sec- 
  

   tions, 
  does 
  not 
  essentially 
  differ 
  from 
  that 
  of 
  the 
  embryo 
  just 
  before 
  

   hatching, 
  as 
  the 
  interval 
  is 
  apparently 
  too 
  short 
  for 
  a 
  decided 
  change 
  to 
  

   take 
  place. 
  It 
  is 
  evident 
  that 
  by 
  the 
  end 
  of 
  the 
  first 
  larval 
  stage 
  the 
  

   brain 
  attains 
  the 
  development 
  seen 
  in 
  the 
  third 
  larval 
  state 
  of 
  the 
  two- 
  

   banded 
  species. 
  

  

  For 
  illustrations 
  of 
  the 
  different 
  larval 
  and 
  pupal 
  stages 
  of 
  develop- 
  

   ment 
  of 
  the 
  locust 
  the 
  reader 
  is 
  referred 
  to 
  the 
  first 
  Eeport 
  of 
  the 
  Com- 
  

   mission 
  (Plates 
  I, 
  II, 
  III). 
  

  

  Third 
  larval 
  stage 
  of 
  Caloptenus 
  bivittatus 
  (PI. 
  XIII, 
  Fig. 
  1-3). 
  — 
  In 
  the 
  

   third 
  larval 
  condition 
  of 
  another 
  species, 
  the 
  common 
  Caloptenus 
  bivit- 
  

   tatus 
  of 
  our 
  gardens, 
  the 
  different 
  parts 
  of 
  the 
  brain 
  have 
  attained 
  

   nearly 
  the 
  same 
  structure 
  and 
  proportions 
  as 
  in 
  the 
  adult. 
  PI. 
  XIII, 
  

   Fig. 
  1, 
  represents 
  a 
  section 
  passing 
  through 
  the 
  front 
  of 
  the 
  brain, 
  and 
  

   also 
  the 
  lateral 
  ocelli 
  and 
  the 
  right 
  eye. 
  The 
  ganglion 
  cells 
  surrounding 
  

   and 
  filling 
  the 
  calices 
  are 
  smaller 
  and 
  more 
  crowded 
  than 
  elsewhere. 
  

   The 
  mushroom 
  bodies 
  are 
  now 
  formed, 
  though 
  the 
  trabecule 
  are 
  not 
  to 
  

   be 
  seen 
  in 
  our 
  section, 
  but 
  the 
  entire 
  double 
  stalk 
  and 
  calices 
  are 
  very 
  

   clearly 
  seen. 
  The 
  fibers 
  from 
  the 
  stalk 
  are 
  observed 
  to 
  extend 
  along 
  

   the 
  inner 
  edge 
  of 
  each 
  calyx 
  and 
  to 
  suddenly 
  stop 
  just 
  beyond 
  the 
  mid- 
  

   dle. 
  The 
  granular 
  calices 
  contain 
  slight 
  irregularities 
  and 
  sinuous 
  lines, 
  

   as 
  shown 
  in 
  Fig. 
  2, 
  i. 
  cat., 
  o 
  ca., 
  but 
  to 
  what 
  these 
  appearances 
  are 
  due 
  

   it 
  is 
  difficult 
  to 
  say 
  ; 
  there 
  are 
  also 
  a 
  few 
  scattered 
  large 
  granules. 
  As 
  

   the 
  section 
  passes 
  through 
  the 
  front 
  of 
  the 
  brain, 
  where 
  the 
  hemispheres 
  

   are 
  separated 
  by 
  the 
  frontal 
  furrow, 
  the 
  lobes 
  are 
  not 
  well 
  marked, 
  but 
  

   the 
  substance 
  is 
  made 
  up 
  of 
  irregular 
  intercrossing 
  bundles 
  of 
  fibers, 
  

   with 
  the 
  interspaces 
  filled 
  with 
  granulated 
  matter. 
  In 
  Fig. 
  3 
  the 
  regu- 
  

   lar 
  saucer-like 
  form 
  of 
  the 
  calyx 
  is 
  well 
  shown. 
  Fig. 
  2 
  is 
  an 
  enlarged 
  

   view 
  of 
  the 
  right 
  side 
  of 
  Fig. 
  1, 
  and 
  at 
  this 
  stage 
  large 
  important 
  bundles 
  

   of 
  fibers 
  are 
  seen 
  passing 
  into 
  the 
  optic, 
  antennal, 
  and 
  commissural 
  

   lobes. 
  

  

  