﻿AIR-TIBKS 
  OF 
  THE 
  LOCUST. 
  

  

  191 
  

  

  Traohew.—The 
  trachea 
  of 
  insects 
  have 
  long 
  attracted 
  the 
  attention 
  of 
  

   comparative 
  anatomists, 
  and 
  the 
  curious 
  spiral 
  thread 
  which 
  lies 
  within 
  

   their 
  interior 
  has 
  been 
  frequently 
  mentioned 
  both 
  by 
  the 
  older 
  as 
  well 
  

   as 
  the 
  more 
  recent 
  writers. 
  Those 
  who 
  wish 
  to 
  become 
  acquainted 
  with 
  

   the 
  opinions 
  of 
  the 
  authors 
  of 
  the 
  beginning 
  of 
  this 
  century, 
  will 
  find 
  a 
  

   capital 
  summary 
  in 
  Shuckard's 
  Burmeister, 
  p. 
  170. 
  It 
  may 
  also 
  be 
  

   well 
  to 
  state 
  that 
  the 
  trachea; 
  do 
  not 
  consist 
  of 
  an 
  " 
  external 
  serous 
  and 
  

   internal 
  mucous 
  membrane," 
  as 
  quoted 
  by 
  Dr. 
  Packard 
  on 
  pp. 
  40-41 
  of 
  

   his 
  invaluable 
  "Guide 
  to 
  the 
  Study 
  of 
  Insects," 
  that 
  idea 
  of 
  their 
  struc- 
  

   ture 
  bemg 
  now 
  known 
  to 
  be 
  incorrect. 
  The 
  true 
  structure 
  of 
  these 
  in- 
  

   teresting 
  air 
  tubes 
  was 
  not 
  known 
  until 
  1875, 
  when 
  Dr. 
  Chun 
  one 
  of 
  

   Leuckart's 
  pupils, 
  published 
  an 
  article*" 
  on 
  the 
  « 
  Rectaldrusen 
  'der 
  In- 
  

   secten," 
  in 
  which 
  he 
  incidentally 
  describes 
  with 
  approximate 
  exactitude 
  

  

  Fig. 
  6.— 
  Testis 
  otAnabrus, 
  showing 
  the 
  ramifications 
  of 
  the 
  trachea). 
  

  

  I 
  the 
  structure 
  of 
  the 
  tracheae. 
  Leydig*« 
  had 
  previously 
  found 
  that 
  the 
  

   ■ 
  mner 
  membrane 
  consists 
  of 
  two 
  layers, 
  and 
  that 
  the 
  spiral 
  filaments 
  are 
  

   | 
  not 
  distinct 
  and 
  separate, 
  but, 
  on 
  the 
  contrary, 
  intimatelv 
  connected 
  with 
  

   : 
  the 
  inner 
  membrane. 
  Leydig 
  also 
  found 
  the 
  trachese 
  to 
  have 
  an 
  outer 
  

  

  layer, 
  which 
  contained 
  nuclei, 
  and 
  which 
  he 
  wrongly 
  supposed 
  to 
  be 
  con- 
  

   : 
  nective 
  tissue, 
  even 
  venturing 
  to 
  say 
  that 
  no 
  one 
  could 
  think 
  of 
  regard- 
  

   j 
  ing 
  it 
  as 
  an 
  epithelium. 
  Chun, 
  in 
  his 
  paper 
  above 
  cited, 
  was 
  the 
  first 
  to 
  

  

  show 
  that 
  Leydig 
  was 
  in 
  error 
  in 
  making 
  this 
  statement, 
  and 
  that, 
  in 
  a 
  

  

  variety 
  of 
  insects, 
  the 
  cellular 
  matrix, 
  which 
  secretes 
  the 
  inner 
  membrane 
  

   i 
  and 
  the 
  spiral 
  thread, 
  is 
  really 
  an 
  epithelium. 
  At 
  the 
  same 
  time 
  I 
  made 
  

  

  similar 
  observations 
  on 
  various 
  insects, 
  particularly 
  on 
  the 
  large 
  water 
  

  

  'inTe 
  k 
  tT 
  ; 
  Ahl%l^ 
  

  

  »i«,X 
  Jtt 
  t 
  * 
  "* 
  Nat 
  '? 
  rach 
  ; 
  6 
  «- 
  Frankfnrt, 
  1876, 
  Bd. 
  x, 
  p. 
  27. 
  Stmotur 
  der 
  Trscheen. 
  p. 
  39. 
  

   ThiefS, 
  K^ers 
  ft 
  "" 
  ' 
  ' 
  "* 
  »' 
  "* 
  ^^ 
  te 
  ***** 
  P 
  ' 
  386 
  ' 
  V 
  ° 
  m 
  Bai 
  d 
  <° 
  

  

  