﻿278 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  head: 
  oue 
  in 
  eacli 
  tlioracic 
  segment, 
  and 
  one 
  in 
  each 
  of 
  the 
  ten 
  abdomi- 
  

   nal 
  segments. 
  

  

  There 
  are 
  two 
  main 
  tracheal 
  stems 
  indicated 
  at 
  this 
  date, 
  the 
  tracheae 
  

   at 
  this 
  time 
  consisting 
  of 
  masses 
  of 
  yolk 
  globules. 
  In 
  nearly 
  each 
  segment 
  

   are 
  smaller 
  connecting 
  branches, 
  while 
  small 
  branches 
  pass 
  oatward 
  from 
  

   the 
  outer 
  tracheal 
  stem 
  {tr') 
  to 
  the 
  stigmata. 
  I^o 
  branches 
  were 
  traced 
  

   into 
  the 
  head, 
  and 
  the 
  two 
  main 
  trunks 
  appeared 
  to 
  be 
  united 
  in 
  the 
  

   fourth 
  cephalic 
  segment, 
  where 
  they 
  expand, 
  and 
  at 
  the 
  end 
  of 
  the 
  abdo- 
  

   men 
  they 
  unite 
  in 
  the 
  ninth 
  segment. 
  The 
  stigmata 
  were 
  small, 
  with 
  a 
  

   central 
  depression, 
  the 
  area 
  of 
  invagination. 
  

  

  The 
  most 
  interesting 
  feature 
  at 
  this 
  stage 
  is 
  the 
  primitive 
  mouth 
  or 
  

   oesophagus 
  and 
  fore-stomach 
  or 
  stomodceum 
  {st). 
  This 
  is 
  seen 
  to 
  be 
  a 
  

   sac, 
  the 
  result 
  of 
  invagination, 
  and 
  it 
  has 
  a 
  double 
  wall, 
  with 
  the 
  square 
  

   mouth 
  opening 
  at 
  the 
  anterior 
  end. 
  The 
  notch 
  behind 
  the 
  mouth 
  may 
  

   possibly 
  be 
  the 
  point 
  where 
  the 
  rudimentary 
  proventriculus 
  begins. 
  The 
  

   primitive 
  intestine 
  or 
  proctodceum 
  (pr)^ 
  has 
  the 
  same 
  structure 
  appar- 
  

   ently 
  as 
  the 
  stomodceum. 
  There 
  was 
  no 
  appearance 
  at 
  this 
  stage 
  of 
  a 
  

   mid-gut 
  or 
  mesenteron. 
  At 
  the 
  back 
  part 
  of 
  the 
  head 
  was 
  a 
  mass 
  of 
  

   yolk 
  cells 
  extending 
  from 
  near 
  the 
  posterior 
  part 
  of 
  the 
  stomodseum 
  

   outwards 
  towards 
  the 
  outer 
  edge 
  of 
  the 
  mandibular 
  segment. 
  This 
  mass 
  

   of 
  cells 
  (Fig. 
  1, 
  sal) 
  I 
  am 
  disposed 
  to 
  regard 
  as 
  the 
  first 
  indications 
  of 
  

   the 
  salivary 
  glands. 
  

  

  PI. 
  XYIII, 
  Fig. 
  3, 
  represents 
  the 
  fore-head 
  or 
  pre- 
  oral 
  part 
  of 
  the 
  head 
  

   of 
  another 
  embryo, 
  with 
  the 
  eyes 
  a 
  little 
  more 
  advanced, 
  and 
  showing 
  

   the 
  anterior 
  ocellus 
  (oc) 
  and 
  the 
  oesophageal 
  part 
  of 
  the 
  stomodaium. 
  

  

  PI. 
  XVI, 
  Fig. 
  2, 
  shows 
  the 
  structure 
  of 
  the 
  body 
  walls, 
  being 
  the 
  epithe- 
  

   lium 
  forming 
  the 
  integument 
  of 
  the 
  side 
  of 
  a 
  segment, 
  formed 
  by 
  a 
  

   single 
  row 
  of 
  oval 
  epithelial 
  cells. 
  Fig. 
  3 
  represents 
  the 
  structure 
  of 
  

   the 
  inner 
  embryonal 
  membrane 
  or 
  "amnion," 
  some 
  of 
  the 
  blastoderm 
  

   cells 
  being 
  distinctly 
  nucleated. 
  

  

  February 
  2. 
  A 
  more 
  advanced 
  embryo 
  was 
  observed 
  in 
  process 
  of 
  

   turning. 
  PI. 
  XYIII, 
  Fig. 
  2, 
  represents 
  the 
  head 
  and 
  thorax 
  at 
  this 
  time. 
  

   The 
  eyes 
  are 
  now 
  reddish 
  and 
  far 
  advanced. 
  The 
  three 
  ganglia 
  suc- 
  

   ceeding 
  the 
  brain 
  are 
  also 
  to 
  be 
  seen. 
  

  

  In 
  an 
  embryo 
  observed 
  February 
  5, 
  — 
  perhaps, 
  however, 
  not 
  so 
  far 
  

   advanced 
  as 
  the 
  preceding, 
  — 
  the 
  structure 
  of 
  the 
  eyes 
  could 
  be 
  observed. 
  

   PI. 
  XVI, 
  Fig. 
  4, 
  is 
  a 
  natural 
  section 
  through 
  the 
  eye 
  as 
  seen 
  in 
  the 
  living 
  

   embryo. 
  The 
  cones 
  are 
  seen 
  to 
  be 
  oval-o^long 
  cells, 
  with 
  a 
  distinct 
  

   nucleus 
  ; 
  each 
  cone 
  is 
  succeeded 
  by 
  the 
  rod, 
  and 
  at 
  a 
  short 
  distance 
  

   from 
  the 
  cone 
  is 
  the 
  indication 
  of 
  the 
  retina 
  (ret), 
  a 
  reddish 
  mass 
  not 
  

   continuously 
  extended 
  from 
  rod 
  to 
  rod, 
  each 
  mass 
  with 
  a 
  dark 
  distinct 
  

   nucleus. 
  

  

  The 
  origin 
  of 
  the 
  ocelli 
  is 
  now 
  to 
  be 
  seen. 
  PI. 
  XVI, 
  Fig. 
  5e, 
  represents 
  

   a 
  vertical 
  view 
  of 
  the 
  procephalic 
  lobes, 
  with 
  the 
  indications 
  of 
  the 
  three 
  

   ocelli. 
  Each 
  ocellus 
  is 
  seen 
  to 
  be 
  formed 
  of 
  several 
  (6 
  or 
  7) 
  reddish 
  pig- 
  

   ment 
  cells. 
  PI. 
  X 
  Vlll, 
  Fig. 
  4, 
  shows 
  clearly 
  the 
  relations 
  of 
  the 
  antenna 
  

  

  