﻿110 
  E. 
  J. 
  ALLEN. 
  

  

  with 
  an 
  intermediate 
  substance^ 
  much 
  of 
  which 
  is 
  clearly 
  made 
  

   up 
  of 
  a 
  feltwork 
  of 
  fine 
  fibres. 
  The 
  whole 
  structure 
  exactly 
  

   esembles 
  what 
  is 
  fouud 
  in 
  parts 
  of 
  the 
  brain 
  and 
  the 
  ventral 
  

   nerve-cord. 
  In 
  many 
  sections 
  fine 
  fibres 
  can 
  be 
  clearly 
  seen 
  

   passing 
  from 
  this 
  ganglionic 
  mass 
  to 
  the 
  hair-bearing 
  cells 
  

   (fig. 
  34). 
  The 
  exact 
  relations 
  of 
  these 
  fibres 
  to 
  the 
  latter 
  

   cells 
  could 
  not 
  be 
  determined. 
  

  

  The 
  Protruding 
  Lateral 
  Organs 
  of 
  the 
  Anterior 
  

   Segments. 
  — 
  Fig. 
  o9 
  (PI. 
  10) 
  shows 
  a 
  section 
  through 
  one 
  of 
  

   the 
  protruding 
  organs 
  of 
  the 
  anterior 
  segments, 
  the 
  external 
  

   views 
  of 
  which 
  are 
  seen 
  in 
  figs. 
  2, 
  3, 
  4, 
  and 
  5 
  (PL 
  7). 
  The 
  

   structure 
  is 
  essentially 
  the 
  same 
  as 
  that 
  of 
  the 
  organs 
  already 
  

   described, 
  but 
  the 
  various 
  parts 
  are 
  packed 
  more 
  closely 
  

   together, 
  so 
  that 
  the 
  details 
  are 
  less 
  easily 
  made 
  out. 
  No 
  

   further 
  description 
  is, 
  however, 
  necessary. 
  

  

  Connection 
  with 
  the 
  Central 
  Nervous 
  System. 
  — 
  

   The 
  ganglion 
  of 
  each 
  lateral 
  organ 
  receives 
  a 
  bundle 
  of 
  fibres 
  

   from 
  a 
  nerve 
  which 
  passes 
  up 
  the 
  body-wall 
  from 
  the 
  ganglion 
  

   of 
  the 
  ventral 
  nerve-cord. 
  The 
  course 
  of 
  this 
  nerve 
  can 
  be 
  

   easily 
  followed 
  in 
  sections, 
  its 
  fibres 
  lying 
  immediately 
  

   beneath 
  the 
  cells 
  of 
  the 
  epidermis, 
  between 
  these 
  cells 
  and 
  the 
  

   muscular 
  layers 
  of 
  the 
  body-wall. 
  After 
  giving 
  off 
  the 
  branch 
  

   to 
  the 
  ganglion 
  of 
  the 
  lateral 
  organ 
  the 
  nerve 
  continues 
  its 
  

   course 
  in 
  a 
  dorsal 
  direction, 
  and 
  has 
  been 
  definitely 
  traced 
  as 
  

   far 
  as 
  the 
  notopodial 
  cirrus. 
  

  

  Muscles. 
  — 
  The 
  muscles 
  attached 
  to 
  the 
  apex 
  of 
  the 
  lateral 
  

   organs 
  are 
  described 
  on 
  p. 
  125. 
  

  

  Historical. 
  — 
  The 
  first 
  detailed 
  description 
  of 
  the 
  structure 
  

   of 
  the 
  lateral 
  sense-organs 
  of 
  Pplycheetes 
  was 
  given 
  by 
  Eisig 
  

   (1879 
  and 
  1887), 
  who 
  studied 
  them 
  in 
  the 
  Capitellids. 
  There 
  

   are 
  some 
  differences 
  of 
  importance 
  between 
  Eisig's 
  account 
  

   of 
  the 
  minute 
  structure 
  of 
  the 
  organs 
  in 
  Capitellids 
  and 
  the 
  

   description 
  of 
  what 
  is 
  fouud 
  in 
  Pcecilochostus 
  set 
  forth 
  in 
  

   the 
  present 
  paper. 
  In 
  Capitellids 
  Eisig 
  describes 
  a 
  layer 
  of 
  

   rods 
  immediately 
  under 
  the 
  chitin, 
  and 
  this 
  is 
  followed 
  by 
  an 
  

   irregularly 
  arranged 
  layer 
  of 
  spindle-shaped 
  bodies. 
  The 
  

   layer 
  of 
  rods 
  would 
  seem 
  to 
  correspond 
  Avitli 
  the 
  long 
  rods 
  in 
  

  

  