﻿220 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  tudinal 
  and 
  external 
  circular 
  coat 
  ; 
  the 
  fibres 
  are 
  all 
  striped. 
  The 
  lining 
  

   epithelium 
  is 
  not 
  much 
  developed, 
  but 
  forms 
  a 
  thick, 
  hard, 
  and 
  very 
  re- 
  

   fringent 
  cuticula 
  that 
  is 
  thrown 
  up 
  into 
  ridges, 
  that 
  may 
  be 
  armed 
  with 
  

   spines. 
  The 
  chitinous 
  lining, 
  or 
  the 
  cuticula, 
  is 
  undoubtedly 
  always 
  

   secreted 
  by 
  an 
  epithelium, 
  314 
  and 
  does 
  not 
  belong 
  in 
  the 
  series 
  of 
  con- 
  

   nective 
  tissues, 
  as 
  Leydig 
  has 
  maintained. 
  315 
  It 
  will 
  be 
  seen 
  that 
  these 
  

   features 
  are 
  common 
  to 
  all 
  the 
  subdivisions 
  of 
  the 
  anterior 
  segment 
  of 
  the 
  

   digestive 
  canal, 
  the 
  principal 
  variations 
  being 
  in 
  the 
  form 
  and 
  develop- 
  

   ment 
  of 
  the 
  ridges, 
  and 
  the 
  muscular 
  layers, 
  as 
  I 
  have 
  already 
  described 
  

   in 
  detail. 
  The 
  thick 
  cuticula 
  of 
  the 
  <•< 
  Vorderdarm" 
  has 
  been 
  observed 
  

   in 
  many 
  insects, 
  316 
  and 
  of 
  all 
  orders. 
  

  

  The 
  second 
  division 
  of 
  the 
  alimentary 
  canal 
  is 
  distinguished 
  from 
  the 
  

   first 
  by 
  the 
  epithelium 
  being 
  composed 
  of 
  very 
  high 
  cylindrical 
  cells, 
  

   which 
  make 
  up 
  the 
  greater 
  part 
  of 
  the 
  thickness 
  of 
  the 
  walls 
  ; 
  by 
  the 
  pres- 
  

   ence 
  of 
  a 
  very 
  delicate, 
  and 
  but 
  slightly 
  refringent, 
  cuticula, 
  and 
  the 
  ab- 
  

   sence 
  of 
  ridges 
  ; 
  by 
  the 
  unstriated 
  muscular 
  coats, 
  and, 
  finally, 
  by 
  the 
  

   development 
  of 
  glandular 
  follicles 
  and 
  folds. 
  The 
  ventricle 
  and 
  divert- 
  

   icula 
  have 
  all 
  these 
  peculiarities 
  in 
  common, 
  while 
  no 
  other 
  part 
  of 
  the 
  

   digestive 
  canal 
  resembles 
  them 
  in 
  the 
  least. 
  Essentially 
  the 
  same 
  pe- 
  

   culiarities 
  distinguish 
  the 
  "Mitteldarm" 
  of 
  Phthirius 
  inguinalis, 
  Leach 
  317 
  , 
  

   except 
  that 
  there 
  are 
  no 
  glandular 
  follicles. 
  Landois 
  318 
  has 
  wrongly 
  ho- 
  

   mologized 
  this 
  part 
  with 
  the 
  crop 
  of 
  the 
  Orthoptera. 
  

  

  The 
  third 
  division 
  (intestine 
  and 
  rectum) 
  has 
  an 
  epithelium, 
  the 
  cells 
  

   of 
  which 
  are 
  intermediate 
  in 
  size 
  between 
  those 
  of 
  the 
  first 
  and 
  second 
  

   division. 
  The 
  cells 
  are 
  often 
  pigmented 
  5 
  they 
  are 
  covered 
  by 
  a 
  cuticu- 
  

   la 
  much 
  firmer 
  than 
  that 
  of 
  the 
  ventricle, 
  but 
  not 
  so 
  thick 
  and 
  hard 
  as 
  

   that 
  of 
  the 
  first 
  division. 
  The 
  very 
  refringent 
  cuticula 
  is 
  not 
  trans- 
  

   formed 
  into 
  ridges, 
  though 
  in 
  some 
  parts 
  it 
  is 
  covered 
  with 
  delicate 
  

   conical 
  spines, 
  which 
  are 
  very 
  short. 
  The 
  epithelium 
  and 
  underlying 
  

   connective 
  tissue 
  (tunica 
  propria) 
  are 
  thrown 
  up 
  into 
  six 
  folds, 
  which 
  

   run 
  longitudinally, 
  being 
  regular 
  in 
  the 
  ileum 
  and 
  rectum 
  (as 
  the 
  rectal 
  

   glands), 
  but 
  very 
  irregular 
  in 
  the 
  colon. 
  Outside 
  the 
  depression 
  between 
  

   «ach 
  two 
  neighboring 
  folds 
  there 
  is 
  a 
  longitudinal 
  muscular 
  band, 
  thus 
  

   making 
  six 
  bands. 
  This 
  peculiar 
  disposition 
  of 
  the 
  longitudinal 
  muscles 
  

   does 
  not 
  occur 
  in 
  any 
  other 
  part 
  of 
  the 
  canal 
  ; 
  it 
  is 
  therefore 
  especially 
  

   eharacteristic 
  of 
  the 
  third 
  division. 
  From 
  this 
  statement 
  of 
  the 
  charac- 
  

   teristics 
  of 
  the 
  three 
  divisions, 
  it 
  is 
  evident 
  that 
  the 
  gastroileal 
  valves 
  

   belong 
  to 
  the 
  third. 
  

  

  The 
  curious 
  repetition 
  of 
  the 
  number 
  six 
  may 
  be 
  pointed 
  out 
  here. 
  I 
  

   cannot 
  but 
  think 
  it 
  will 
  be 
  ultimately 
  found 
  to 
  have 
  some 
  hitherto 
  un- 
  

   suspected 
  meaning. 
  There 
  are 
  six 
  rows 
  of 
  teeth 
  in 
  the 
  proventriculus, 
  

  

  314 
  Semper: 
  Ueber 
  die 
  Entstehung 
  der 
  Scliuppen 
  bei 
  den 
  Lepidopteren. 
  Zeit 
  Wias.Zool., 
  VTEL 
  Cf. 
  

   •also, 
  Gegenbaur, 
  Chun, 
  Braun, 
  et 
  al. 
  

   " 
  6 
  Leydig: 
  Vom 
  Bau 
  dea 
  Thierschen 
  Korpors, 
  p. 
  38, 
  ff. 
  

   816 
  For 
  example 
  : 
  Phthirius 
  inguinalis 
  Leach. 
  Graber. 
  Z. 
  Z. 
  XXII, 
  141. 
  

   ™Graber: 
  Zeit. 
  Wiss., 
  Zool. 
  XXII, 
  142-144. 
  

   3 
  '8 
  Landois 
  : 
  Zeit. 
  Wise. 
  Zool, 
  XIV, 
  p. 
  1, 
  and 
  XV, 
  502. 
  

  

  