﻿THE 
  ANATOMY 
  OP 
  P(ECIL00H7ETUS, 
  CLAPAHEDE. 
  89 
  

  

  The 
  third 
  segment 
  resembles 
  the 
  second, 
  excepting 
  tliat 
  the 
  

   cirri 
  are 
  slightly 
  smaller 
  and 
  more 
  conical 
  in 
  shape, 
  and 
  there 
  

   is 
  not 
  quite 
  such 
  a 
  tendency 
  for 
  them 
  to 
  be 
  directed 
  forwards. 
  

   The 
  neuropodial 
  chsetge 
  consist 
  of 
  three 
  well-developed 
  and 
  one 
  

   rudimentary 
  stout 
  hooks 
  and 
  a 
  few 
  fine 
  hairs, 
  all 
  as 
  in 
  seg- 
  

   ment 
  2 
  (PI. 
  7, 
  fig. 
  2). 
  The 
  notopodial 
  chfetas 
  are 
  all 
  smooth 
  

   hairs, 
  no 
  spiny 
  bristles 
  like 
  those 
  in 
  segment 
  2 
  being 
  present. 
  

  

  In 
  the 
  fourth 
  segment 
  the 
  cirri 
  are 
  not 
  quite 
  so 
  large 
  as 
  in 
  

   the 
  third, 
  and 
  are 
  usually 
  directed 
  outwards 
  or 
  slightly 
  back- 
  

   wards. 
  The 
  cheetae 
  of 
  the 
  neuropodium 
  are 
  no 
  longer 
  stout 
  

   hooks, 
  but 
  form 
  a 
  bundle 
  of 
  straight, 
  smooth 
  bristles, 
  similar 
  

   to 
  those 
  of 
  the 
  notopodium. 
  There 
  are 
  no 
  spiny 
  bristles. 
  

  

  The 
  fifth 
  segment 
  (figs. 
  1, 
  3, 
  and 
  7) 
  differs 
  from 
  its 
  

   neighbours 
  in 
  the 
  fact 
  that 
  the 
  neuropodial 
  cirri 
  are 
  short, 
  

   whilst 
  the 
  notopodial 
  cirri 
  are 
  long 
  and 
  slender, 
  being 
  the 
  

   longest 
  ciri'i, 
  with 
  the 
  exception 
  of 
  those 
  on 
  the 
  first 
  segment, 
  

   which 
  are 
  found 
  on 
  the 
  whole 
  body 
  of 
  the 
  worm 
  (fig. 
  3). 
  

   These 
  two 
  long 
  cirri 
  are 
  also 
  often 
  carried 
  in 
  a 
  somewhat 
  

   different 
  position 
  from 
  those 
  on 
  other 
  parts 
  of 
  the 
  body, 
  

   being 
  arched 
  over 
  the 
  back 
  of 
  the 
  worm. 
  

  

  The 
  sixth 
  segment 
  closely 
  resembles 
  the 
  fourth 
  (fig. 
  1), 
  the 
  

   cirri 
  being 
  generally 
  directed 
  backwards. 
  The 
  chastae 
  from 
  

   the 
  third 
  to 
  the 
  sixth 
  segment 
  are 
  all 
  smooth 
  hairs, 
  amongst 
  

   which 
  no 
  spiny 
  bristles 
  are 
  found. 
  

  

  Segments 
  1 
  to 
  6 
  may 
  be 
  considered 
  as 
  constituting 
  the 
  

   first 
  sub-division 
  of 
  the 
  anterior 
  region 
  of 
  the 
  body. 
  With 
  

   segment 
  7 
  a 
  change 
  takes 
  place, 
  which 
  is 
  expressed 
  both 
  

   in 
  the 
  external 
  and 
  internal 
  structure 
  of 
  the 
  worm. 
  Ex- 
  

   ternally 
  — 
  that 
  is 
  to 
  say, 
  regarded 
  from 
  the 
  point 
  of 
  view 
  of 
  

   the 
  structure 
  of 
  the 
  parapodia 
  only 
  — 
  the 
  second 
  sub-division 
  of 
  

   the 
  body 
  would 
  seem 
  to 
  comprise 
  the 
  segments 
  from 
  the 
  seventh 
  

   to 
  the 
  thirteenth, 
  but, 
  as 
  will 
  be 
  shown 
  later 
  (p. 
  139), 
  this 
  does 
  

   not 
  quite 
  agree 
  with 
  the 
  division 
  indicated 
  by 
  the 
  internal 
  

   anatomy, 
  which 
  points 
  rather 
  to 
  segments 
  7 
  to 
  11 
  only 
  being 
  

   classed 
  together. 
  

  

  The 
  peculiarity 
  of 
  the 
  parapodia 
  of 
  segments 
  7 
  to 
  13 
  (figs. 
  

   4 
  and 
  5) 
  lies 
  in 
  the 
  form 
  and 
  structure 
  of 
  the 
  notopodial 
  and 
  

  

  VOL. 
  48, 
  PART 
  1. 
  NEW 
  SERIES. 
  7 
  

  

  