﻿302 
  W. 
  BLAXLAND 
  BEN 
  HAM. 
  

  

  The 
  oesophagus 
  is 
  quite 
  a 
  narrow 
  tube, 
  lined 
  by 
  ciliated 
  

   epithelium, 
  which 
  is 
  somewhat 
  folded 
  ; 
  it 
  passes 
  backwards, 
  

   below 
  the 
  sperra-sacs, 
  as 
  far 
  as 
  Segment 
  XII, 
  where 
  it 
  is 
  

   slightly 
  dilated, 
  and 
  the 
  ventral 
  wall 
  thrown 
  into 
  folds, 
  

   which 
  are 
  more 
  vascular 
  than 
  elsewhere. 
  

  

  As 
  to 
  the 
  vascular 
  system, 
  the 
  dorsal 
  and 
  ventral 
  vessels 
  

   are 
  connected 
  by 
  a 
  pair 
  of 
  undulating 
  " 
  commissural 
  vessels 
  " 
  

   in 
  every 
  segment, 
  as 
  in 
  the 
  other 
  two 
  species 
  of 
  the 
  genus. 
  

  

  Nephridia. 
  — 
  The 
  first 
  nephridium 
  occurs 
  in 
  Segment 
  X, 
  

   with 
  a 
  funnel 
  in 
  the 
  preceding 
  segment 
  ; 
  none 
  are 
  present 
  in 
  

   the 
  following 
  three 
  segments, 
  in 
  which 
  the 
  genital 
  ducts 
  lie, 
  

   but 
  in 
  Segment 
  XIV 
  and 
  in 
  each 
  of 
  the 
  subsequent 
  segments 
  

   there 
  is 
  a 
  pair 
  of 
  excretory 
  organs, 
  and 
  these 
  are 
  larger 
  

   than 
  those 
  in 
  the 
  tenth 
  segment. 
  

  

  In 
  the 
  immature 
  individual 
  likewise 
  no 
  nephridia 
  are 
  to 
  

   be 
  seen 
  in 
  the 
  Segments 
  XI, 
  XII, 
  XIII. 
  

  

  In 
  H. 
  gordioides 
  Forbes 
  (4) 
  finds 
  rudimentary 
  nephridia 
  

   in 
  all 
  the 
  genital 
  segments 
  of 
  a 
  quite 
  immature 
  individual 
  in 
  

   which 
  no 
  trace 
  of 
  genital 
  organs 
  are 
  yet 
  present. 
  

  

  The 
  disposition 
  and 
  structure 
  of 
  the 
  nephridium 
  is 
  illus- 
  

   trated 
  in 
  figs. 
  3 
  — 
  8. 
  The 
  nephridia! 
  funnel 
  of 
  the 
  post-ovarian 
  

   organ, 
  at 
  least, 
  has 
  the 
  usual 
  form, 
  with 
  one 
  lip 
  a 
  good 
  deal 
  

   higher 
  than 
  the 
  other 
  (fig. 
  9) 
  ; 
  the 
  canal, 
  after 
  piercing 
  the 
  

   septum, 
  perforates 
  a 
  row 
  of 
  vesicular 
  cells, 
  which 
  form 
  a 
  

   loose 
  loop. 
  The 
  cytoplasm 
  of 
  these 
  cells 
  exhibits 
  (when 
  

   studied 
  under 
  a 
  yV 
  homogeneous 
  immersion 
  lens) 
  a 
  faint 
  

   network, 
  but 
  immediately 
  around 
  the 
  canal 
  this 
  network 
  

   is 
  replaced 
  by 
  more 
  closely 
  granulated 
  protoplasm, 
  which 
  

   forms 
  a 
  distinct 
  but 
  narrow 
  "wall" 
  to 
  the 
  canal 
  (fig. 
  8). 
  

  

  These 
  cells 
  do 
  not 
  correspond 
  with 
  the 
  vesicular 
  "peritoneal 
  

   cells" 
  that 
  surround 
  the 
  nephridium 
  in 
  certain 
  earthworms, 
  

   or 
  which 
  occur, 
  for 
  instance, 
  in 
  Psammoryctes, 
  as 
  figured 
  

   by 
  Vejdovsky. 
  

  

  find 
  that 
  Micliaelsen 
  (5) 
  has 
  already 
  described 
  this 
  r^izzard 
  in 
  H. 
  gordioides 
  

   in 
  much 
  the 
  same 
  terms 
  as 
  I 
  have 
  above 
  used. 
  In 
  this 
  paper 
  he 
  corrects 
  

   several 
  errors 
  and 
  niisconce))tions 
  in 
  tlie 
  description 
  of 
  the 
  various 
  " 
  species" 
  

   of 
  Hap 
  lot 
  axis, 
  and 
  sliows 
  tiiat 
  the 
  European 
  and 
  American 
  species 
  are 
  

   identical. 
  

  

  