﻿114 
  E. 
  J. 
  ALLEN. 
  

  

  Immediately 
  inside 
  the 
  cuticle 
  is 
  a 
  narrow 
  zone, 
  which 
  in 
  

   sections 
  appears 
  clear, 
  but 
  across 
  which 
  the 
  cilia 
  can 
  be 
  seen 
  

   to 
  pass. 
  This 
  zone 
  may, 
  to 
  some 
  extent 
  at 
  least, 
  be 
  due 
  to 
  

   shrinkage 
  of 
  the 
  bodies 
  of 
  the 
  cells 
  during 
  preservation 
  and 
  

   their 
  consequent 
  withdrawal 
  from 
  the 
  cuticle. 
  It 
  is 
  followed 
  by 
  

   what, 
  in 
  transverse 
  sections, 
  appears 
  as 
  a 
  deeply 
  staining 
  line 
  

   (stained 
  red 
  in 
  methyl-blue-eosin 
  preparations). 
  This 
  line, 
  on 
  

   examination 
  with 
  high 
  powers, 
  resolves 
  itself 
  into 
  a 
  layer 
  of 
  

   deeply 
  staining, 
  short 
  rods 
  (lig.41,6r.),oue 
  rod 
  apparently 
  corre- 
  

   sponding 
  with 
  each 
  cilium. 
  Within 
  this 
  layer 
  of 
  deeply 
  staining 
  

   rods 
  the 
  internal 
  ends 
  of 
  the 
  cilia 
  can 
  be 
  followed 
  for 
  a 
  consider- 
  

   able 
  distance 
  as 
  faintly 
  staining 
  rods 
  (blue 
  in 
  methyl-blue- 
  

   eosin 
  preparations), 
  the 
  diameters 
  of 
  which 
  appear 
  somewhat 
  

   greater 
  than 
  the 
  diameters 
  of 
  the 
  cilia 
  outside 
  the 
  body 
  (fig. 
  

   41, 
  I. 
  r.). 
  In 
  the 
  portion 
  of 
  the 
  cell 
  occupied 
  by 
  these 
  rods 
  

   the 
  protoplasm 
  of 
  the 
  cell 
  appears 
  clear, 
  and 
  not 
  granular 
  as 
  

   it 
  does 
  throughout 
  the 
  general 
  body 
  of 
  the 
  cell. 
  These 
  rela- 
  

   tions 
  will 
  be 
  seen 
  to 
  correspond 
  with 
  those 
  found 
  in 
  the 
  

   ciliated 
  cells 
  of 
  the 
  wall 
  of 
  the 
  oesophagus 
  (p. 
  117, 
  et 
  seq., 
  

   whei'e 
  the 
  work 
  of 
  previous 
  authors 
  is 
  discussed, 
  PI. 
  11, 
  fig. 
  44) 
  

   and 
  in 
  the 
  hair-bearing 
  cells 
  of 
  the 
  lateral 
  organs 
  (p. 
  108, 
  

   PL 
  10, 
  figs. 
  ;j4, 
  30, 
  39). 
  

  

  In 
  the 
  nuchal 
  organ 
  of 
  Poecilochajtus, 
  I 
  have 
  failed 
  to 
  

   identify 
  nerve-cells, 
  other 
  than 
  the 
  ganglion-cells 
  already 
  

   described 
  in 
  the 
  basal 
  portion 
  of 
  the 
  organ. 
  It 
  is 
  quite 
  

   possible, 
  however, 
  that 
  some 
  of 
  the 
  cells 
  of 
  the 
  intermediate 
  

   tissue 
  are 
  really 
  such 
  nerve-cells. 
  

  

  For 
  a 
  full 
  historical 
  account 
  of 
  the 
  nuchal 
  organ 
  in 
  Poly- 
  

   chseta, 
  as 
  well 
  as 
  for 
  an 
  excellent 
  description 
  of 
  the 
  detailed 
  

   histological 
  structure 
  of 
  that 
  organ 
  in 
  a 
  number 
  of 
  different 
  

   types, 
  reference 
  should 
  be 
  made 
  to 
  the 
  paper 
  by 
  Racovitza 
  

   (1896) 
  already 
  several 
  times 
  mentioned. 
  

  

  Eyes. 
  

  

  As 
  previously 
  stated, 
  Poecilochaetus 
  possesses 
  four 
  eyes, 
  

   one 
  pair 
  on 
  the 
  dorsal 
  surface 
  of 
  the 
  prostomium, 
  and 
  a 
  

  

  