﻿ECHIUROID 
  WORMS 
  OF 
  NORTH 
  PACIFIC 
  — 
  FISHER 
  263 
  

  

  includinE: 
  a 
  lonf;: 
  frizzard 
  botwoon 
  an 
  anterior 
  lonp: 
  crop 
  and 
  a 
  posterior 
  

   long 
  stoniacli; 
  proboscis 
  reducetl 
  to 
  a 
  scoop-sha})ed 
  ii])per 
  lip. 
  

  

  Genus 
  URECHIS 
  Seitz 
  

  

  Urechis 
  Seitz, 
  1907, 
  p. 
  352 
  (type, 
  Echiiirus 
  chilensis 
  Max 
  Miiller, 
  1852). 
  — 
  Fisher 
  

  

  and 
  MacGinitik, 
  1928a, 
  p. 
  200. 
  

   Spiroctetor 
  Skorikov, 
  1909, 
  p. 
  77 
  (typo, 
  Echiurus 
  unicincius 
  von 
  Drasche). 
  

  

  Diagnosis. 
  — 
  Cylindrical 
  or 
  sausage-shaped 
  echiuroids 
  with 
  characters 
  

   of 
  family. 
  Body 
  wall 
  is 
  very 
  muscular, 
  consisting 
  of 
  outer 
  and 
  inner 
  

   circular 
  layers 
  and 
  middle 
  longitudinal 
  layer, 
  the 
  latter 
  the 
  thickest; 
  

   inner 
  layer 
  showing 
  a 
  fasciculate 
  arrangement 
  superficially. 
  In 
  the 
  

   region 
  of 
  the 
  posterior 
  pair 
  of 
  nephridia 
  is 
  a 
  zone 
  of 
  compound 
  slime- 
  

   net 
  glands 
  lodged 
  in 
  the 
  verrucae 
  of 
  the 
  skin. 
  There 
  are 
  two 
  or 
  three 
  

   pairs 
  of 
  nephridia, 
  the 
  basal 
  nephrostome 
  of 
  which 
  has 
  long 
  spirally 
  

   coiled 
  ciliated 
  lips 
  for 
  collection 
  of 
  mature 
  germ 
  cells. 
  The 
  two 
  an- 
  

   terior 
  setae 
  have 
  a 
  strong 
  interbasal 
  muscle; 
  one 
  ring 
  of 
  curved 
  anal 
  

   setae 
  interrupted 
  ventrally. 
  Traversing 
  the 
  coelomic 
  cavity 
  in 
  front 
  

   of 
  the 
  anterior 
  setae 
  are 
  paired 
  dorsoventral 
  muscles 
  (pi. 
  34, 
  fig. 
  2, 
  

   13). 
  The 
  alimentary 
  canal 
  has 
  a 
  definite 
  pattern 
  of 
  attachment 
  to 
  

   body 
  wall 
  by 
  muscular 
  mesenteries, 
  difTering 
  in 
  minor 
  details 
  in 
  the 
  

   three 
  species 
  (pi. 
  35, 
  fig. 
  1). 
  The 
  slender 
  foregut 
  is 
  very 
  extensive, 
  

   consisting 
  of 
  pharynx, 
  esophagus, 
  crop 
  (subtended 
  by 
  a 
  powerful 
  

   muscular 
  mesentery 
  not 
  attached 
  to 
  body), 
  a 
  long 
  gizzard, 
  and 
  a 
  

   stomach 
  attached 
  posteriorly 
  by 
  a 
  strong 
  mesentery. 
  The 
  greater 
  

   part 
  of 
  the 
  very 
  long 
  midgut 
  is 
  accompanied 
  by 
  the 
  siphon, 
  which 
  

   starts 
  close 
  to 
  distal 
  end 
  of 
  stomach. 
  The 
  ciliated 
  groove 
  of 
  midgut, 
  

   which 
  parallels 
  the 
  siphon, 
  extends 
  be3'ond 
  it 
  to 
  the 
  point 
  where 
  the 
  

   gut 
  is 
  suddenl}' 
  expanded 
  mto 
  the 
  inflatable 
  respiratory 
  portion. 
  The 
  

   external 
  ridge 
  marking 
  the 
  ciliated 
  groove 
  continues 
  along 
  dorsal 
  

   side 
  of 
  this 
  expansion, 
  passing 
  distally 
  to 
  the 
  right 
  where 
  it 
  afi'ords 
  

   attachment 
  for 
  mesenteries, 
  but 
  there 
  is 
  no 
  groove 
  inside 
  corresj)ond- 
  

   ing 
  to 
  it. 
  This 
  inflatable 
  so-called 
  "hind-gut" 
  is 
  equivalent 
  to 
  the 
  

   terminal 
  part 
  of 
  the 
  midgut 
  of 
  Kchiurus 
  (wliich 
  is 
  not 
  enlarged). 
  

   The 
  only 
  similar 
  abrupt 
  enlargement 
  occurs 
  in 
  Nellobia 
  eusoina. 
  The 
  

   true 
  hind-gut 
  or 
  cloacal 
  cavity 
  is 
  separated 
  from 
  the 
  foregoing 
  by 
  a 
  

   definite 
  s{)liincter 
  constriction 
  and 
  consists 
  of 
  a 
  thin-walled 
  ant(>rior 
  

   liortion 
  and 
  a 
  thicker-walled 
  terminal 
  section 
  willi 
  rugose 
  mucosa. 
  

   Verj' 
  numerous 
  frenula 
  attach 
  cloaca 
  to 
  body 
  wall 
  and 
  account 
  for 
  

   tlie 
  exj)ansion 
  of 
  cavity 
  l)y 
  which 
  water 
  is 
  inhaled 
  din-ing 
  respiration. 
  

   The 
  anal 
  vesicles 
  are 
  voluminous, 
  slender 
  sacs, 
  always 
  deflated, 
  which 
  

   open 
  ventrally 
  into 
  terminal 
  portion 
  of 
  cloaca. 
  The 
  glandular 
  walls 
  

   are 
  externally 
  rather 
  cauliflowerlike 
  and 
  the 
  entire 
  inner 
  surface 
  is 
  

   intricately 
  plicated. 
  The 
  scattered 
  ciliated 
  funnels 
  arc 
  veiy 
  tiny. 
  

   The 
  anus 
  is 
  eccentric 
  to 
  the 
  circle 
  of 
  setae, 
  being 
  slightly 
  nearer 
  the 
  

   ventral 
  side 
  fpl. 
  33, 
  fig. 
  4). 
  

  

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