﻿222 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

   MALPIGHIAN 
  VESSELS. 
  

  

  The 
  vasa 
  varicosa 
  of 
  Malpighi 
  have 
  long 
  attracted 
  the 
  attention 
  and 
  

   excited 
  the 
  interest 
  of 
  naturalists. 
  The 
  earliest 
  histological 
  description 
  

   of 
  them, 
  however, 
  with 
  which 
  I 
  am 
  acquainted, 
  is 
  comparatively 
  recent 
  — 
  

   I 
  refer 
  to 
  the 
  article 
  of 
  H. 
  Meckel. 
  321 
  Since 
  then 
  three 
  general 
  accounts 
  

   of 
  their 
  structure 
  have 
  been 
  published, 
  one 
  very 
  full 
  by 
  Sirodot, 
  322 
  and 
  

   another 
  by 
  Leydig, 
  323 
  and 
  the 
  third 
  and 
  most 
  important 
  by 
  Schindler, 
  32 
  * 
  

   and 
  they 
  have 
  been 
  investigated 
  by 
  numerous 
  other 
  anatomists 
  in 
  a 
  

   great 
  many 
  insects. 
  

  

  Their 
  structure 
  is 
  very 
  much 
  the 
  same 
  in 
  the 
  grasshopper 
  as 
  in 
  the 
  

   cockroach. 
  325 
  They 
  are 
  covered 
  by 
  a 
  delicate 
  external 
  envelope 
  (tunica 
  

   propria) 
  , 
  Figs. 
  40, 
  41, 
  47, 
  48, 
  in 
  which 
  there 
  occasionally 
  appear 
  small 
  

   nuclei. 
  They 
  are 
  lined 
  by 
  flattened 
  epithelial 
  cells 
  with 
  granular 
  con- 
  

   tents 
  and 
  large 
  oval 
  nuclei, 
  which 
  leave 
  a 
  round 
  central 
  cavity, 
  Fig. 
  40. 
  

   The 
  canal, 
  as 
  observed 
  in 
  optical 
  section, 
  Fig. 
  47, 
  is 
  not 
  straight, 
  but 
  

   somewhat 
  sinuous 
  in 
  its 
  course. 
  Seen 
  in 
  transverse 
  section, 
  the 
  out- 
  

   lines 
  of 
  the 
  cells, 
  Fig. 
  40, 
  resemble 
  those 
  of 
  truncated 
  cones. 
  There 
  

   are 
  generally 
  four 
  rows 
  of 
  cells 
  around 
  the 
  inner 
  canal, 
  as 
  indicated 
  in 
  

   Fig. 
  40. 
  Some 
  parts 
  of 
  the 
  vessels 
  are 
  surcharged 
  with 
  reddish-brown 
  

   pigment 
  granules. 
  The 
  tubes 
  are, 
  as 
  is 
  well 
  known, 
  not 
  of 
  the 
  same 
  

   diameter 
  throughout 
  their 
  length, 
  but 
  consist 
  of 
  a 
  narrower 
  and 
  a 
  wider 
  

   portion. 
  The 
  Figs. 
  40, 
  42, 
  47, 
  48 
  all 
  represent 
  the 
  narrower 
  part. 
  In 
  

   the 
  segment 
  with 
  the 
  greater 
  diameter 
  the 
  thickness 
  of 
  the 
  walls 
  remain 
  

   about 
  the 
  same, 
  so 
  that 
  the 
  " 
  lumen 
  77 
  of 
  the 
  vessel 
  is 
  increased. 
  The 
  

   nuclei 
  are 
  larger 
  and 
  more 
  nearly 
  round 
  instead 
  of 
  oval. 
  

  

  321 
  Meckel, 
  1. 
  c, 
  Miiller's 
  Archiv. 
  1846, 
  p. 
  41 
  ff. 
  

  

  322 
  S. 
  Sirodot: 
  Becherches 
  sur 
  les 
  S6cr6tions 
  chez 
  les 
  Insects. 
  Ann. 
  Sci. 
  Nat. 
  Zool. 
  Ser. 
  IV. 
  Tome 
  x 
  

   (1858), 
  p. 
  251. 
  Histologic 
  p. 
  268. 
  

  

  323 
  Leydig: 
  Lehrbnch 
  der 
  Histologic, 
  p. 
  464, 
  §426. 
  

  

  324 
  J;. 
  Schindler 
  : 
  Beitrage 
  zur 
  Kenntniss 
  der 
  malpighischen 
  G-efasse 
  der 
  Insecten. 
  Zeit. 
  f. 
  wisa. 
  ZooL, 
  

   Bd. 
  xxx. 
  (1878), 
  p. 
  587. 
  

   326 
  Basch. 
  1. 
  c. 
  Sitzber. 
  Wien 
  Akad. 
  xxxiii. 
  (1858), 
  p. 
  254. 
  

  

  