﻿DEVELOPMENT 
  OF 
  CALOPTENUS 
  SPEETUS. 
  277 
  

  

  enlarging 
  into 
  amcebiform 
  or 
  triangular 
  masses 
  at 
  the 
  corners 
  between 
  

   the 
  polygonal 
  yolk-balls. 
  From 
  these 
  thin 
  walls 
  fibers 
  are 
  sent 
  off 
  to 
  

   the 
  rounded 
  nuclei 
  within, 
  with 
  which 
  are 
  also 
  associated 
  scattered 
  an- 
  

   gular 
  masses 
  {an). 
  We 
  judge 
  from 
  these 
  tvTO 
  sets 
  of 
  bodies, 
  the 
  rounded 
  

   and 
  the 
  amcebiform, 
  that 
  the 
  nuclei 
  of 
  the 
  yolk 
  cells 
  are 
  in 
  an 
  active 
  

   state 
  of 
  proliferation. 
  

  

  A 
  peculiarity 
  in 
  the 
  relation 
  of 
  the 
  yolk 
  granules 
  to 
  one 
  another 
  we 
  

   have 
  never 
  seen 
  mentioned. 
  They 
  appear 
  to 
  be 
  attached 
  to 
  the 
  yolk- 
  cell- 
  

   wall 
  by 
  very 
  slender 
  pedicels 
  or 
  fibers, 
  sometimes 
  as 
  many 
  as 
  five 
  or 
  six 
  

   such 
  fine 
  strings 
  or 
  fibers 
  holding 
  the 
  larger 
  granules 
  in 
  place 
  j 
  while 
  

   those 
  granules 
  in 
  the 
  interior 
  of 
  the 
  yolk 
  cell 
  are 
  attached 
  to 
  each 
  other 
  

   by 
  slender 
  fibers. 
  The 
  granules 
  are 
  more 
  numerous 
  in 
  the 
  center 
  of 
  

   the 
  yolk 
  cell 
  than 
  near 
  the 
  periphery. 
  These 
  fibers, 
  like 
  the 
  granules 
  

   themselves, 
  are 
  not 
  stained 
  by 
  picro-carmine; 
  the 
  yolk 
  granules 
  are 
  also 
  

   colorless, 
  not 
  receiving 
  a 
  stain, 
  being 
  filled 
  with 
  a 
  clear 
  fluid, 
  and 
  are 
  

   not 
  sufiiciently 
  numerous 
  to 
  be 
  crowded 
  together, 
  hence 
  they 
  retain 
  

   their 
  original 
  spherical 
  form. 
  

  

  We 
  were 
  unable 
  in 
  our 
  sections 
  of 
  0. 
  atlanis 
  to 
  detect 
  any 
  entoblas- 
  

   tic 
  or 
  mesoblastic 
  cells, 
  either 
  free 
  in 
  the 
  yolk 
  or 
  in 
  layers. 
  

  

  II. 
  Development 
  of 
  Caloptenus 
  spretus. 
  

  

  ' 
  I 
  received 
  in 
  the 
  winter 
  of 
  1881 
  a 
  mass 
  of 
  eggs 
  taken 
  from 
  the 
  earth 
  

   at 
  Nephi, 
  Utah, 
  January 
  7, 
  which 
  had 
  been 
  deposited 
  the 
  previous 
  

   autumn. 
  They 
  were 
  kept 
  in 
  a 
  sunny 
  room 
  heated 
  from 
  60° 
  to 
  70^ 
  F. 
  

  

  Plate 
  XYII, 
  Fig. 
  1, 
  1 
  a 
  represents 
  the 
  earliest 
  stage 
  (observed 
  January 
  

   26, 
  1881). 
  At 
  this 
  time 
  the 
  embryo 
  lay 
  on 
  one 
  side 
  of 
  the 
  yolk, 
  but 
  not 
  

   immersed 
  in 
  it, 
  the 
  primitive 
  segments 
  decreasing 
  in 
  size 
  from 
  the 
  pro- 
  

   cephalic 
  lobes 
  to 
  the 
  end 
  of 
  the 
  abdomen. 
  The 
  embryonal 
  membranes 
  

   are 
  not 
  indicated 
  in 
  the 
  figures. 
  The 
  procephalic 
  lobes 
  are 
  nearly 
  as 
  

   long 
  as 
  deep, 
  and 
  the 
  eyes 
  are 
  already 
  indicated. 
  The 
  head 
  is 
  seen 
  to 
  

   be 
  composed 
  of 
  two 
  regions, 
  the 
  procephalic 
  lobes, 
  and 
  the 
  tergal 
  por- 
  

   tion 
  of 
  a 
  second 
  segment. 
  This 
  segment 
  we 
  are 
  disposed 
  to 
  regard 
  

   as 
  the 
  fourth 
  (second 
  maxillary 
  or 
  labial), 
  and 
  it 
  may 
  be 
  compared 
  with 
  

   the 
  very 
  distinct 
  fourth 
  cephalic 
  arthromere 
  of 
  Diplax,'^^ 
  a 
  dragon 
  fly. 
  Of 
  

   the 
  tbree 
  thoracic 
  segments 
  the 
  last 
  is 
  rather 
  longer 
  than 
  the 
  others. 
  

  

  Plate 
  XYI, 
  Fig. 
  1 
  (observed 
  January 
  28), 
  represents 
  a 
  more 
  advanced 
  

   embryo, 
  which 
  had 
  been 
  removed 
  from 
  the 
  egg 
  and 
  slipped 
  out 
  upon 
  the 
  

   surface 
  of 
  a 
  live-box. 
  The 
  nervous 
  system, 
  consisting 
  of 
  the 
  brain 
  and 
  

   succeeding 
  ganglia, 
  is 
  now 
  clearly 
  indicated, 
  as 
  are 
  also 
  the 
  tracheal 
  sys- 
  

   tem 
  and 
  spiracles. 
  

  

  As 
  regards 
  the 
  nervous 
  system, 
  the 
  brain 
  and 
  optic 
  ganglia 
  are 
  indi- 
  

   cated 
  j 
  the 
  eyes 
  begin 
  to 
  show 
  a 
  reddish 
  tint. 
  The 
  ganglia 
  of 
  the 
  ventral 
  

   chain 
  are 
  14 
  or 
  15 
  in 
  all, 
  including 
  the 
  brain, 
  as 
  better 
  seen 
  in 
  PI. 
  XVII, 
  

   Fig. 
  2, 
  than 
  in 
  the 
  present 
  figure. 
  Thus 
  there 
  are 
  two 
  ganglia 
  in 
  the 
  

  

  issErabryological 
  Studies 
  on 
  Diplax, 
  Perithemis, 
  and 
  tbe 
  Tbysannroiis 
  genus 
  Isotoma. 
  By 
  A. 
  S. 
  

   Packard, 
  jr. 
  Memoirs 
  Peabody 
  Academy 
  of 
  Science, 
  1871. 
  PI. 
  2, 
  Fig. 
  9,^. 
  

  

  