﻿92 
  E. 
  J. 
  ALLEN. 
  

  

  each 
  parapodium, 
  one 
  pair 
  being 
  attached 
  to 
  the 
  posterior 
  

   face 
  of 
  the 
  neuropodium 
  and 
  one 
  pair 
  to 
  the 
  posterior 
  face 
  of 
  

   the 
  notopodiain. 
  

  

  The 
  terminal 
  segments 
  (PL 
  8, 
  fig-. 
  6) 
  show 
  certain 
  special 
  

   features. 
  The 
  general 
  shape 
  of 
  the 
  body 
  is 
  here 
  flattened, 
  

   and 
  the 
  dorsal 
  surface 
  is 
  somewhat 
  concave. 
  The 
  neuropodial 
  

   and 
  notopodial 
  cirri 
  are 
  of 
  about 
  the 
  normal 
  shape, 
  but 
  the 
  

   neuropodial 
  is 
  double 
  the 
  size 
  of 
  the 
  notopodial, 
  and 
  the 
  latter 
  

   assumes 
  a 
  more 
  dorsal 
  position 
  than 
  usual. 
  The 
  more 
  dorsal 
  

   of 
  the 
  notopodial 
  chgetae 
  are 
  transformed 
  into 
  strong 
  hooks 
  

   (figs. 
  6 
  and 
  19), 
  which 
  form 
  a 
  transverse 
  row 
  on 
  either 
  side 
  of 
  

   the 
  dorsal 
  surface 
  of 
  the 
  segment. 
  Five 
  or 
  six 
  such 
  hooks 
  

   are 
  generally 
  found 
  on 
  each 
  notopodium. 
  The 
  curve 
  of 
  the 
  

   hook 
  is 
  directed 
  backwards, 
  and 
  those 
  nearest 
  the 
  middle 
  line 
  

   are 
  the 
  stoutest 
  as 
  well 
  as 
  the 
  most 
  strongly 
  curved. 
  These 
  

   hooks 
  are 
  found 
  on 
  the 
  last 
  sixteen 
  or 
  seventeen 
  segments 
  

   (in 
  full-grown 
  specimens), 
  and 
  obviously 
  serve 
  the 
  purpose 
  of 
  

   enabling 
  the 
  worm 
  to 
  hold 
  itself 
  firmly 
  in 
  the 
  tube. 
  

  

  The 
  remaining 
  cha)t{e 
  of 
  the 
  notopodium 
  and 
  those 
  of 
  the 
  

   neuropodium 
  in 
  these 
  segments 
  are 
  mostly 
  either 
  of 
  the 
  

   ordinaiy 
  smooth 
  or 
  spiny 
  kinds, 
  the 
  latter 
  being 
  often 
  

   rudimentary. 
  There 
  is 
  also 
  found, 
  in 
  the 
  terminal 
  region 
  of 
  

   the 
  body 
  a 
  special 
  kind 
  of 
  bristle 
  not 
  met 
  with 
  elsewhere 
  

   (PI. 
  9, 
  fig. 
  18). 
  This 
  consists 
  of 
  a 
  stout, 
  smooth 
  shaft, 
  

   showing 
  longitudinal 
  striations, 
  and 
  ending 
  in 
  a 
  blunt 
  tooth 
  

   directed 
  slightly 
  outwards. 
  From 
  the 
  base 
  of 
  this 
  tooth 
  there 
  

   arises 
  a 
  hairy 
  terminal 
  portion 
  of 
  the 
  bristle, 
  which 
  forms 
  a 
  

   kind 
  of 
  flexible 
  brush 
  attached 
  to 
  the 
  end 
  of 
  the 
  stiff 
  shaft. 
  

   Bristles 
  of 
  this 
  character 
  are 
  a 
  modified 
  form 
  of 
  the 
  ordinary 
  

   stout, 
  haii*y 
  bristles, 
  which, 
  as 
  the 
  end 
  of 
  the 
  body 
  is 
  

   approached, 
  at 
  first 
  lose 
  the 
  hairs 
  along 
  the 
  greater 
  part 
  of 
  

   the 
  length 
  of 
  the 
  shaft, 
  retaining 
  them 
  only 
  at 
  the 
  ends. 
  The 
  

   type 
  of 
  bristle 
  with 
  the 
  hairy 
  flexible 
  end 
  (fig. 
  18) 
  becomes 
  

   established 
  at 
  about 
  the 
  thirtieth 
  segment 
  from 
  the 
  end 
  of 
  the 
  

   body 
  (in 
  full-grown 
  specimens), 
  and 
  occurs 
  in 
  the 
  segments 
  

   from 
  this 
  point 
  to 
  about 
  the 
  ninth 
  or 
  tenth 
  from 
  the 
  end. 
  

  

  In 
  the 
  terminal 
  segments 
  the 
  lateral 
  sense-organs 
  have 
  

  

  