﻿PLATE 
  XII. 
  

  

  Fig. 
  1. 
  Section 
  No. 
  7 
  of 
  brain 
  of 
  embryo 
  C. 
  spretus, 
  earliest 
  stage 
  observed, 
  passing 
  

   through 
  the 
  upper 
  and 
  lower 
  cerebral 
  (embryonic) 
  lobes 
  (up. 
  I., 
  low. 
  I.'). 
  

   (Do 
  the 
  upper 
  cerebral 
  lobes 
  become 
  the 
  calices 
  and 
  the 
  lower 
  cerebral 
  lobes 
  

   ultimately 
  become 
  the 
  trabecular?) 
  (See 
  fig. 
  8 
  ; 
  low. 
  I.), 
  op. 
  I., 
  optic 
  lobe; 
  

   ant. 
  I., 
  antennal 
  lobe 
  ; 
  eye, 
  outline 
  of 
  the 
  eyes 
  ; 
  X 
  i, 
  Tolles's 
  objective, 
  A 
  eye- 
  

   piece. 
  

  

  Fig. 
  la. 
  Portion 
  of 
  the 
  left 
  upper 
  cerebral 
  lobe 
  of 
  fig. 
  1, 
  magnified 
  400 
  diameters, 
  

   showing 
  the 
  gradual 
  passage 
  of 
  the 
  cortical 
  ganglion 
  cells 
  into 
  the 
  central 
  

   granular 
  nervous 
  substance, 
  the 
  granules 
  (gran.) 
  extending 
  and 
  filling 
  up 
  

   the 
  spaces 
  between 
  the 
  nucleated 
  ganglion 
  cells 
  (gang, 
  c.) 
  ; 
  it 
  will 
  be 
  noticed 
  

   that 
  there 
  are 
  at 
  this 
  time 
  no 
  nervous 
  fibers. 
  

  

  Fig. 
  2. 
  Section 
  No. 
  5 
  of 
  head 
  of 
  a 
  more 
  advanced 
  embryo, 
  just 
  ready 
  to 
  hatch, 
  the 
  

   section 
  not 
  including 
  any 
  part 
  of 
  the 
  brain, 
  the 
  cells 
  represented 
  being 
  con- 
  

   nective-tissue 
  cells 
  enveloping 
  the 
  brain. 
  The 
  portions 
  left 
  blank 
  in 
  figs. 
  

   1, 
  7, 
  and 
  9 
  are 
  in 
  the 
  actual 
  sections 
  filled 
  with 
  similar 
  connective-tissue 
  

   (mesodermic) 
  cells. 
  

  

  Fig. 
  3. 
  Section 
  No. 
  6 
  of 
  the 
  same 
  embryo, 
  passing 
  through 
  the 
  optic 
  and 
  antennal 
  

   lobes. 
  

  

  Fig. 
  4. 
  Section 
  No. 
  7 
  of 
  the 
  same, 
  passing 
  through 
  the 
  "upper 
  cerebral 
  lobes" 
  or 
  

   calices 
  of 
  the 
  future 
  mushroom 
  body 
  (cer. 
  I.), 
  and 
  also 
  through 
  the 
  optic 
  and 
  

   antennal 
  lobes. 
  

  

  Fig. 
  5. 
  Section 
  No. 
  8, 
  passing 
  through 
  the 
  brain 
  (next 
  behind 
  No. 
  7). 
  

  

  Fig. 
  6. 
  Section 
  No. 
  9, 
  passing 
  Ihrough 
  what 
  is 
  probably 
  (?) 
  the 
  mushroom 
  body 
  

   marked 
  as 
  the 
  cerebral 
  lobe 
  (cer. 
  I.). 
  

  

  Fig. 
  7. 
  Section 
  No. 
  10. 
  The 
  parts 
  not 
  well 
  defined. 
  

  

  Fig. 
  8. 
  Section 
  No. 
  11, 
  through 
  the 
  brain 
  of 
  the 
  same 
  embryo 
  as 
  figs. 
  2-7, 
  and 
  passing 
  

   through 
  the 
  upper 
  and 
  lower 
  cerebral 
  lobes, 
  and 
  the 
  central 
  body 
  (cent. 
  &.), 
  at 
  

   this 
  point 
  clearly 
  indicated. 
  Probably 
  the 
  "lower 
  cerebral 
  lobes 
  " 
  become 
  

   the 
  trabecules 
  of 
  the 
  adult 
  insect. 
  The 
  sections 
  do 
  not 
  enable 
  us 
  to 
  deter- 
  

   mine 
  with 
  exactitude 
  the 
  history 
  of 
  the 
  embryonic 
  upper 
  and 
  lower 
  cerebral 
  

   lobes. 
  (For 
  enlarged 
  views 
  of 
  the 
  upper 
  and 
  lower 
  cerebral 
  lobes 
  and 
  the 
  

   central 
  body 
  see 
  Plate 
  xiii, 
  fig. 
  4) 
  ; 
  int. 
  indicates 
  the 
  integument 
  of 
  the 
  head. 
  

  

  Fig. 
  9. 
  Section 
  No. 
  12 
  of 
  the 
  same 
  embryo 
  : 
  up. 
  I., 
  upper, 
  low. 
  1., 
  lower, 
  cerebral 
  lobes 
  ; 
  

   038., 
  cEsophagus 
  (compare 
  also 
  figs. 
  6 
  and 
  7 
  of 
  Plate 
  xiii, 
  representing 
  sec- 
  

   tions 
  behind 
  the 
  head 
  of 
  the 
  same 
  embryo). 
  

  

  Fig. 
  10. 
  Section 
  No. 
  6 
  of 
  the 
  younger 
  embryo, 
  passing 
  in 
  front 
  of 
  No. 
  7, 
  fig. 
  1, 
  of 
  this 
  

  

  plate, 
  and 
  representing 
  the 
  subcesophageal 
  ganglion, 
  showing 
  the 
  form 
  of 
  

  

  the 
  ganglion 
  and 
  the 
  relation 
  of 
  the 
  central 
  granular 
  nervous 
  matter 
  (gran.) 
  

  

  to 
  the 
  envelope 
  of 
  cortical 
  cells 
  (gang. 
  c. 
  ) 
  ; 
  X 
  i, 
  Tolles's 
  objective, 
  B 
  eye-piece. 
  

  

  Figs. 
  2-9 
  were 
  drawn 
  with 
  the 
  same 
  objective, 
  A 
  eye-piece. 
  

  

  