﻿276 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  the 
  glandular 
  la^^er 
  finally 
  becoming 
  a 
  single 
  row 
  of 
  amniotic 
  cells 
  which 
  

   pass 
  up 
  dorsally 
  towards 
  and 
  finally 
  appear 
  to 
  surround 
  a 
  cavity 
  {do?) 
  

   which 
  may 
  possibly 
  be 
  the 
  remnants 
  of 
  the 
  '^dorsal 
  plate" 
  of 
  Kowa- 
  

   levsky 
  and 
  Dohrn 
  (see 
  Balfour's 
  Comparative 
  ]^mbryology, 
  i, 
  p. 
  335, 
  Fig. 
  

   185. 
  Our 
  sections 
  are 
  here 
  imperfect, 
  leaving 
  a 
  doubt 
  in 
  my. 
  mind 
  

   whether 
  the 
  organ 
  {dof) 
  is 
  not 
  formed 
  by 
  a 
  growing 
  up 
  of 
  the 
  ectoblast, 
  

   as 
  Dohrn 
  states, 
  towards 
  the 
  dorsal 
  region, 
  forming 
  a 
  provisional 
  tube. 
  

   It 
  is 
  doubtful 
  whether 
  at 
  this 
  stage 
  the 
  heart 
  reaches 
  as 
  far 
  back 
  as 
  the 
  

   proctodseumj 
  and 
  the 
  sections 
  in 
  front 
  (Figs. 
  3, 
  4, 
  5) 
  show 
  the 
  heart 
  very 
  

   clearly, 
  with 
  a 
  thick, 
  definite 
  wall, 
  and 
  situated 
  next 
  to 
  the 
  serous 
  mem- 
  

   brane. 
  On 
  the 
  other 
  hand, 
  the 
  tube-like 
  organ 
  (dof) 
  is 
  less 
  glandular, 
  

   with 
  much 
  thinner 
  walls 
  than 
  indicated 
  by 
  Kowalevsky's 
  figures. 
  

  

  The 
  urinary 
  tubes. 
  — 
  At 
  this 
  stage 
  the 
  urinary 
  or 
  Malxjighiau 
  tubes 
  

   are 
  clearly 
  indicated 
  (Fig. 
  6 
  ut) 
  as 
  arising 
  from 
  the 
  anterior 
  end 
  of 
  the 
  

   incipient 
  intestine 
  or 
  proctodaeum. 
  In 
  the 
  section 
  representee} 
  by 
  Fig. 
  

   6, 
  the 
  microtome 
  passed 
  through 
  the 
  end 
  of 
  the 
  proctodseum, 
  in 
  which 
  

   the 
  two 
  sub-layers, 
  the 
  inner 
  or 
  glandular 
  {gl) 
  and 
  the 
  outer 
  or 
  fibrous 
  

   (fl)^ 
  are 
  clearly 
  indicated, 
  the 
  origins 
  of 
  at 
  least 
  eight, 
  and 
  possibly 
  

   ten, 
  of 
  these 
  tubes 
  were 
  observed. 
  It 
  will 
  be 
  remembered 
  that 
  the 
  

   primitive 
  numberof 
  urinary 
  tubes 
  is 
  four. 
  According 
  to 
  the 
  observations 
  

   of 
  Dohrn, 
  these 
  tubes 
  develop 
  from 
  two 
  primitive 
  pairs 
  of 
  tubes 
  from 
  

   the 
  proctodseum. 
  Hatschek, 
  Taf. 
  Ill, 
  Fig. 
  7, 
  shows 
  the 
  mode 
  of 
  origin 
  

   by 
  budding 
  of 
  the 
  secondary 
  tubes 
  from 
  the 
  primary 
  ones. 
  The 
  urinary 
  

   tubes 
  are 
  plainly 
  seen 
  to 
  be 
  hollow 
  j 
  they 
  are 
  now 
  quite 
  long, 
  as 
  long 
  

   pieces 
  are 
  seen 
  cut 
  oft' 
  and 
  lying 
  about 
  in 
  different 
  places 
  in 
  the 
  section, 
  

   and 
  the 
  microtome 
  also 
  passed 
  through 
  them 
  in 
  section, 
  as 
  seen 
  at 
  ut'. 
  

   Their 
  origin 
  from 
  the 
  glandular 
  layer 
  of 
  the 
  primitive 
  intestine 
  is 
  not 
  

   clearly 
  seen 
  at 
  this 
  stage, 
  as, 
  judging 
  by 
  one 
  section, 
  there 
  is 
  not 
  seen 
  

   to 
  be 
  any 
  close 
  connection 
  at 
  this 
  period 
  with 
  the 
  inner 
  or 
  glandular 
  

   sub-layer 
  of 
  the 
  proctodaeum. 
  

  

  ]^o 
  traces 
  of 
  the 
  sexual 
  glands, 
  that 
  I 
  could 
  discover, 
  appear 
  at 
  this 
  

   stage. 
  

  

  The 
  yolk 
  cells. 
  — 
  At 
  the 
  period 
  represented 
  by 
  Figs. 
  3 
  and 
  5 
  (PI. 
  XX), 
  

   there 
  is 
  seen 
  to 
  be 
  a 
  very 
  fine 
  net- 
  work 
  of 
  irregular, 
  angular, 
  very 
  min- 
  

   ute, 
  masses 
  of 
  protoplasm, 
  which 
  spread 
  through 
  the 
  yolk-mass. 
  In 
  

   some 
  of 
  the 
  triangular 
  masses 
  a 
  minute 
  nucleus-like 
  body 
  not 
  much 
  

   larger 
  than 
  the 
  granules 
  is 
  to 
  be 
  seen. 
  

  

  In 
  close 
  relation 
  with 
  this 
  singular 
  net-w^rk 
  of 
  protoplasm 
  inclosing 
  

   the 
  colossal 
  yolk 
  cells, 
  and 
  which 
  stains 
  a 
  delicate 
  red 
  with 
  picro-car- 
  

   mine, 
  are 
  large, 
  usually 
  rounded 
  masses 
  of 
  protoplasm. 
  They 
  are 
  not, 
  

   however, 
  well-developed 
  cells, 
  but 
  may 
  rather 
  be 
  compared 
  with 
  tlie 
  

   nuclei 
  of 
  cells. 
  Some 
  of 
  them 
  appear 
  to 
  possess 
  a 
  minute 
  nucleolus. 
  We 
  

   regard 
  these 
  as 
  nuclei 
  of 
  the 
  yolk 
  cells, 
  each 
  yolk 
  cell 
  containing 
  from 
  

   about 
  six 
  to 
  eight 
  of 
  them. 
  

  

  Figure 
  5 
  a 
  represents 
  a 
  portion 
  of 
  a 
  yolk-ball 
  with 
  its 
  protoplasmic 
  wall, 
  

  

  