﻿THE 
  ANATOMY 
  OF 
  PCECILOCHM'US, 
  CLAPAREDE. 
  95 
  

  

  are 
  abundant 
  in 
  places. 
  In 
  their 
  simplest 
  form 
  these 
  consist 
  

   of 
  individual 
  cells 
  lying 
  amongst 
  the 
  cells 
  of 
  the 
  epithe- 
  

   lium. 
  One 
  such 
  cell 
  is 
  illustrated 
  in 
  fig. 
  22 
  (PI. 
  10). 
  It 
  

   is 
  pear 
  shaped, 
  with 
  granular 
  protoplasm 
  staining 
  much 
  

   more 
  deeply 
  than 
  that 
  of 
  the 
  surrounding 
  cells, 
  and 
  with 
  an 
  

   oval 
  nucleus, 
  the 
  long 
  axis 
  of 
  which 
  lies 
  parallel 
  to 
  the 
  body 
  

   surface. 
  The 
  protoplasm 
  at 
  the 
  mouth 
  of 
  the 
  cell 
  is 
  inserted 
  

   in 
  a 
  depression 
  on 
  the 
  internal 
  face 
  of 
  the 
  chitin. 
  The 
  

   chitinous 
  tube, 
  which 
  places 
  the 
  interior 
  of 
  the 
  cell 
  in 
  com- 
  

   munication 
  with 
  the 
  external 
  water, 
  forms 
  a 
  conical 
  projection 
  

   on 
  the 
  body 
  surface, 
  and 
  can 
  also 
  be 
  seen 
  to 
  project 
  internally 
  

   for 
  a 
  short 
  distance 
  into 
  the 
  protoplasm 
  of 
  the 
  neck 
  of 
  the 
  

   cell. 
  

  

  Such 
  simple 
  gland-cells 
  are 
  not, 
  however, 
  very 
  numerous. 
  

   The 
  more 
  usual 
  arrangement 
  is 
  for 
  several 
  cells 
  to 
  be 
  asso- 
  

   ciated 
  together 
  and 
  to 
  open 
  externally 
  through 
  one 
  tube. 
  

   Glands 
  of 
  this 
  type 
  are 
  especially 
  numerous 
  in 
  the 
  epithelium 
  

   towards 
  the 
  tail 
  end 
  of 
  the 
  animal, 
  where 
  the 
  tubes 
  are 
  

   situated 
  upon 
  raised 
  chitinous 
  papilla3, 
  which 
  form 
  a 
  character- 
  

   istic 
  featui'e 
  in 
  external 
  views 
  of 
  the 
  animal. 
  These 
  papillae 
  

   and 
  tubes 
  are 
  figured 
  by 
  Claparede 
  (in 
  Ehlers, 
  1874), 
  and 
  

   their 
  great 
  abundance 
  on 
  the 
  dorsal 
  surface 
  of 
  the 
  anterior 
  

   segments 
  in 
  the 
  specimens 
  examined 
  by 
  him 
  constitutes 
  one 
  

   marked 
  difference 
  between 
  his 
  Poecilochaetus 
  fulgoris, 
  

   obtaiued 
  from 
  deep 
  water, 
  and 
  the 
  specimens 
  found 
  at 
  

   Plymouth 
  near 
  low-tide 
  mark 
  on 
  the 
  shore. 
  

  

  A 
  section 
  through 
  such 
  a 
  gland 
  opening 
  on 
  the 
  dorsal 
  

   surface 
  near 
  the 
  tail 
  end 
  of 
  one 
  of 
  the 
  Plymouth 
  specimens 
  is 
  

   shown 
  in 
  fig. 
  23 
  (PI. 
  10). 
  The 
  epithelium 
  here 
  consists 
  of 
  

   flattened 
  cells, 
  with 
  large, 
  oval 
  nuclei. 
  The 
  cuticle 
  is 
  com- 
  

   paratively 
  thin, 
  except 
  in 
  the 
  neighbourhood 
  of 
  the 
  opening 
  

   of 
  the 
  gland. 
  It 
  is 
  there 
  greatly 
  thickened 
  and 
  pushed 
  out- 
  

   wards, 
  forming 
  a 
  tubercle 
  with 
  a 
  stout 
  chitinous 
  covering 
  

   hollowed 
  out 
  internally, 
  the 
  internal 
  hollow 
  being 
  filled 
  with 
  

   the 
  protoplasm 
  of 
  the 
  ends 
  of 
  the 
  gland-cells. 
  Through 
  the 
  

   centre 
  of 
  the 
  tubercle 
  runs 
  the 
  chitinous 
  tube, 
  which 
  places 
  

   the 
  gland-cells 
  in 
  communication 
  with 
  the 
  exterior, 
  the 
  tube 
  

  

  