﻿THE 
  ANATOMY 
  OF 
  PCEOILOOH^ETUS, 
  CLAPAEEDE. 
  97 
  

  

  described, 
  lu 
  the 
  present 
  case^ 
  however, 
  no 
  external 
  openings 
  

   can 
  be 
  demonstrated, 
  unless 
  the 
  radial 
  lines 
  already 
  men- 
  

   tioned 
  really 
  represent 
  pores. 
  Nevertheless 
  an 
  examination 
  

   of 
  a 
  large 
  number 
  both 
  of 
  the 
  gland 
  papillae 
  and 
  of 
  the 
  

   callosities 
  produces 
  a 
  conviction 
  that 
  the 
  latter 
  are 
  in 
  reality 
  

   essentially 
  the 
  same 
  structures 
  as 
  the 
  former, 
  either 
  in 
  a 
  more 
  

   highly 
  developed 
  or 
  in 
  a 
  regenerate 
  state. 
  

  

  The 
  cells 
  lying 
  immediately 
  beneath 
  the 
  tubercle 
  on 
  the 
  

   right-hand 
  side 
  of 
  the 
  section 
  figured 
  (fig. 
  21) 
  are 
  somewhat 
  

   difficult 
  of 
  interpretation. 
  It 
  is 
  possible 
  that 
  the 
  long 
  process 
  

   {j)) 
  immediately 
  beneath 
  the 
  cuticle 
  is 
  homologous 
  with 
  the 
  

   internal 
  portion 
  of 
  the 
  tube 
  of 
  the 
  gland-cells 
  (figs. 
  22 
  and 
  

   23), 
  and 
  that 
  the 
  nucleus 
  (n') 
  is 
  the 
  nucleus 
  ot 
  a 
  gland- 
  

   cell 
  with 
  which 
  this 
  tube 
  communicates. 
  I 
  have 
  not, 
  how- 
  

   ever, 
  found 
  other 
  sections 
  which 
  appear 
  to 
  confirm 
  this 
  

   view. 
  

  

  Although 
  gland-cells 
  are 
  by 
  no 
  means 
  uncommon 
  in 
  the 
  

   general 
  body 
  epithelium, 
  by 
  far 
  the 
  largest 
  development 
  of 
  

   such 
  cells 
  takes 
  place 
  in 
  the 
  dorsal 
  and 
  ventral 
  cirri 
  of 
  the 
  

   parapodia. 
  Fig. 
  25 
  (PI. 
  10), 
  was 
  drawn 
  from 
  one 
  of 
  the 
  cirri 
  

   from 
  the 
  regenerated 
  tail 
  end 
  of 
  a 
  living 
  worm, 
  where 
  the 
  

   transparency 
  of 
  the 
  tissue 
  allowed 
  the 
  gland-cells 
  to 
  be 
  seen. 
  

   Fig. 
  24 
  (PI. 
  10) 
  represents 
  a 
  section 
  through 
  a 
  cirrus 
  from 
  

   about 
  the 
  eighteenth 
  segment 
  of 
  the 
  body. 
  From 
  the 
  latter 
  

   figure 
  it 
  will 
  be 
  seen 
  that 
  a 
  cirrus 
  is 
  crowded 
  with 
  a 
  number 
  of 
  

   flask-shaped 
  cells, 
  the 
  long 
  necks 
  of 
  which 
  open 
  to 
  the 
  exterior 
  

   through 
  papilla3 
  elevated 
  above 
  the 
  surface 
  of 
  the 
  cirrus. 
  (In 
  

   fig. 
  25 
  the 
  long 
  necks 
  of 
  the 
  cells 
  are 
  not 
  shown, 
  the 
  fact 
  that 
  

   they 
  were 
  not 
  visible 
  in 
  the 
  fresh 
  tissue 
  being 
  probably 
  due 
  

   to 
  their 
  great 
  transparency. 
  In 
  fig. 
  24 
  the 
  actual 
  continuity 
  

   between 
  any 
  one 
  cell 
  and 
  the 
  external 
  opening 
  docs 
  not 
  

   appear, 
  but 
  this 
  is 
  quite 
  easily 
  demonstrated 
  in 
  a 
  series 
  of 
  

   sections.) 
  

  

  The 
  gland-cells 
  in 
  the 
  cirri 
  appear 
  under 
  at 
  least 
  three 
  

   forms, 
  which 
  are 
  illustrated 
  in 
  figs. 
  26, 
  27, 
  28, 
  and 
  29 
  

   (PI. 
  10). 
  The 
  figures 
  have 
  been 
  drawn 
  from 
  transverse 
  sec- 
  

   tions 
  of 
  cirri 
  preserved 
  in 
  Hermann's 
  fluid 
  and 
  stained 
  with 
  

  

  