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  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  the 
  walls 
  are 
  contracted. 
  This 
  shows, 
  as 
  I 
  also 
  know 
  from 
  direct 
  obser- 
  

   vation, 
  that 
  the 
  tracheae, 
  though 
  capable 
  of 
  great 
  elongation, 
  are 
  more 
  

   easily 
  bent 
  than 
  compressed, 
  so 
  as 
  to 
  diminish 
  their 
  length. 
  Around 
  

   the 
  organs 
  of 
  more 
  elongated 
  form 
  the 
  branches 
  of 
  the 
  tracheae 
  run 
  

   more 
  longitudinally, 
  as 
  is 
  shown 
  by 
  the 
  air 
  tubes 
  of 
  the 
  muscles, 
  which 
  

   also 
  present 
  some 
  peculiarities 
  worthy 
  of 
  especial 
  notice. 
  A 
  short 
  thick 
  

   trunk 
  (see 
  Fig. 
  12) 
  arrives 
  at 
  the 
  muscular 
  bundle, 
  and, 
  dividing 
  very 
  

   rapidly, 
  breaks 
  up 
  into 
  a 
  large 
  number 
  of 
  delicate 
  tubes, 
  which 
  pene- 
  

   trate 
  between 
  the 
  muscular 
  fibers, 
  there 
  terminating 
  in 
  tubes 
  of 
  exceed- 
  

   ing 
  fineness, 
  which, 
  at 
  first 
  sight, 
  seem 
  to 
  form 
  a 
  network 
  that 
  might 
  

   well 
  be 
  called 
  a 
  rete 
  mirabile. 
  A 
  closer 
  examination, 
  however, 
  reveals 
  

   that 
  it 
  is 
  not 
  a 
  real 
  network, 
  but 
  rather 
  an 
  interlacing, 
  confusing 
  to 
  the 
  

   eye. 
  The 
  longitudinal 
  direction 
  of 
  the 
  tracheae 
  of 
  the 
  muscles 
  presents 
  

   a 
  striking 
  contrast 
  to 
  the 
  system 
  of 
  divarication, 
  represented 
  in 
  Figs. 
  13 
  

   and 
  14. 
  The 
  course 
  of 
  the 
  tracheae 
  of 
  the 
  Malpighian 
  tubes 
  is 
  also 
  very 
  

   curious. 
  It 
  is 
  represented 
  in 
  Fig. 
  10. 
  There 
  is 
  one 
  large 
  trachea 
  which 
  

   winds 
  around 
  the 
  tube 
  in 
  a 
  long 
  spiral, 
  giving 
  off 
  numerous 
  small 
  

   branches, 
  which 
  run 
  to 
  the 
  surface 
  of 
  the 
  tube, 
  upon 
  which 
  they 
  form 
  

   delicate 
  ramifications. 
  Each 
  tube 
  has 
  but 
  a 
  single 
  main 
  trachea, 
  and 
  I 
  

   think 
  the 
  trachea 
  continues 
  the 
  whole 
  length 
  of 
  the 
  tube, 
  but 
  of 
  this 
  last 
  

   point 
  I 
  am 
  not 
  quite 
  sure. 
  

  

  Many 
  organs, 
  as 
  for 
  instance 
  the 
  testis 
  of 
  Anabrus 
  (Fig. 
  6 
  in 
  the 
  text), 
  

   are 
  supplied 
  by 
  a 
  few 
  large 
  tracheal 
  trunks, 
  which 
  give 
  off 
  many 
  small 
  

   branches, 
  the 
  ramifications 
  of 
  which 
  penetrate 
  the 
  organ 
  in 
  question. 
  

  

  The 
  fine 
  terminations 
  of 
  the 
  tracheae 
  have 
  been 
  investigated, 
  as 
  far 
  

   as 
  I 
  am 
  aware, 
  only 
  by 
  Max 
  Schultze, 
  249 
  Weismann, 
  250 
  and 
  H. 
  Meyer. 
  251 
  

  

  They 
  all 
  agree 
  in 
  stating 
  that 
  they 
  end 
  blindly 
  in 
  stellate 
  and 
  branch- 
  

   ing 
  cells. 
  Max 
  Schultze 
  discovered 
  that 
  these 
  terminal 
  cells 
  are 
  dyed 
  

   black 
  by 
  per-osmic 
  acid, 
  so 
  that 
  they 
  are 
  then 
  very 
  sharply 
  marked 
  off 
  

   from 
  all 
  the 
  surrounding 
  tissues. 
  The 
  tracheae 
  extend 
  into 
  the 
  interior 
  

   of 
  these 
  terminal 
  cells. 
  Graber 
  252 
  gives 
  a 
  singular 
  account 
  of 
  the 
  termi- 
  

   nation 
  of 
  the 
  tracheae 
  in 
  Phthirius 
  inguinalis. 
  I 
  cannot 
  but 
  think 
  that 
  

   his 
  description 
  is 
  based 
  upon 
  a 
  false 
  interpretation 
  of 
  his 
  observations. 
  

  

  The 
  development 
  of 
  the 
  tracheae 
  has 
  been 
  studied 
  by 
  Weismann 
  and 
  

   Meyer 
  in 
  the 
  papers 
  just 
  cited, 
  and 
  also 
  by 
  Semper, 
  253 
  in 
  an 
  admirable 
  

   paper 
  on 
  the 
  development 
  of 
  the 
  wings 
  in 
  Lepidoptera. 
  

  

  Dr. 
  Williams, 
  in 
  his 
  article 
  published 
  in 
  the 
  Annals 
  and 
  Magazine 
  of 
  

   Natural 
  History 
  for 
  1854, 
  vol. 
  xiii, 
  maintained 
  that 
  the 
  finer 
  branches 
  

   anastomosed, 
  resembling 
  in 
  that 
  respect 
  the 
  capillaries 
  of 
  vertebrates. 
  

   Lubbock 
  has 
  already 
  pointed 
  out 
  that 
  the 
  tracheal 
  anastomoses 
  are 
  con- 
  

  

  249 
  If 
  as 
  Schultze 
  : 
  Zur 
  Kenntniss 
  dcr 
  Loucbtorgano 
  von 
  Lampyris 
  splendidula. 
  Arch. 
  f. 
  niikros. 
  Anat 
  # 
  

   1, 
  p. 
  124 
  ; 
  Traclieen, 
  p. 
  130, 
  ff. 
  ; 
  figs. 
  4, 
  5, 
  8, 
  and 
  9. 
  

  

  260 
  Weismann 
  : 
  Die 
  Entwickelung 
  dcr 
  Dipteren 
  im 
  Ei. 
  Zeitschrift 
  fur 
  Wisa. 
  Zool. 
  Bd. 
  XIII 
  (18C3), 
  p. 
  193, 
  

  

  251 
  H. 
  Meyer 
  : 
  Uebor 
  die 
  Entwickelung 
  dcs 
  Fettkorpers, 
  der 
  Tracbeen 
  und 
  der 
  koimbereitenden 
  Gcsck- 
  

   locbtstbeilo 
  bci 
  den 
  Lepidopteren. 
  Zeitsch. 
  f. 
  wiss. 
  Zool. 
  Bd. 
  I, 
  p. 
  174. 
  

  

  ™ 
  Graber: 
  Zcit. 
  f. 
  Wiss. 
  Zool. 
  XXII, 
  147 
  (1872). 
  

  

  253 
  Zcit. 
  Wisa. 
  Zool. 
  VIII, 
  p. 
  328. 
  

  

  