﻿ECHIUKOID 
  WUKMS 
  01" 
  XOKTH 
  PACIFIC 
  — 
  FISHER 
  

  

  267 
  

  

  itself 
  is 
  i)robal)ly 
  fibrous 
  in 
  iiaturo, 
  althoutrli 
  this 
  lias 
  not 
  been 
  demon- 
  

   strated. 
  (Figs. 
  17. 
  IS.l 
  

  

  "The 
  body 
  wall 
  consists 
  of 
  the 
  cutich*, 
  the 
  surface 
  epitheliinn 
  or 
  

   epidermis, 
  and 
  the 
  underlyin<; 
  connective 
  tissue 
  called 
  the 
  cutis 
  

   (Jameson, 
  1S99. 
  p. 
  572) 
  or 
  corium 
  (Seitz. 
  1907, 
  p. 
  326). 
  Tliese 
  three 
  

   layers 
  constitute 
  the 
  skin. 
  Beneath 
  tlicni 
  are 
  the 
  outer 
  circular, 
  

   the 
  longitudinal, 
  the 
  inner 
  circular 
  muscle 
  layers 
  and 
  the 
  parietal 
  

   peritoneum." 
  -* 
  

  

  inactive 
  cell-/- 
  

  

  active 
  

  

  cell 
  • 
  ■ 
  / 
  

  

  Figure 
  18. 
  — 
  Urechis 
  caupo 
  Fisher 
  and 
  MacGinitic: 
  A 
  vertical 
  section 
  of 
  the 
  middle 
  part 
  

   of 
  a 
  slimc-nct 
  gland 
  taken 
  while 
  actively 
  secreting; 
  drawing 
  by 
  W. 
  W. 
  Ncwby 
  (1V41). 
  

  

  Anterior 
  setae 
  terminally 
  tapered, 
  sharp, 
  curvetl, 
  situated, 
  in 
  large 
  

   specimens, 
  3 
  to 
  5 
  mm. 
  !)ack 
  of 
  the 
  groove 
  leading 
  to 
  moutli 
  and 
  about 
  

   the 
  same 
  distanec 
  apart. 
  They 
  are 
  metallic 
  yellow, 
  brownish 
  at 
  tip, 
  

   8.5 
  to 
  10.5 
  mm. 
  long. 
  The 
  flattened, 
  curved 
  exserted 
  portion 
  is 
  more 
  

   tapered 
  and 
  sharper 
  than 
  in 
  chilcnsvi. 
  A 
  strong 
  interbasal 
  muscle 
  is 
  

  

  ** 
  Npwl.y, 
  IMI, 
  pp. 
  304. 
  3I.^; 
  flRS. 
  1-10. 
  Dr. 
  Ncwby 
  has 
  subJprto<l 
  the 
  sllmo 
  RlnnMs 
  to 
  a 
  lliorouKh 
  histo 
  

   loKlcnl 
  <itu'ly. 
  He 
  has 
  kindly 
  contributed 
  tho 
  orlRtnal 
  drnwinKS 
  of 
  ORurct 
  17 
  and 
  IN, 
  which 
  arc 
  from 
  the 
  

   alKive 
  paper. 
  

  

  