﻿ECHIUROID 
  WOKMS 
  OF 
  NOUTH 
  PACIFIC 
  — 
  FISHER 
  291 
  

  

  cord; 
  crossiiiu; 
  the 
  ventral 
  mesenteries 
  between 
  the 
  two 
  figure 
  i.{'s 
  is 
  the 
  

   interbasal 
  muscle 
  of 
  setae; 
  radiating 
  muscles 
  of 
  setae 
  shown 
  in 
  solid 
  black 
  

   on 
  right. 
  

  

  3, 
  Anterior 
  ainpoct 
  of 
  a 
  nephridium 
  of 
  second 
  pair 
  showing 
  nephrostome 
  and 
  

  

  elongated 
  lips 
  spirally 
  coiled, 
  X 
  5. 
  

  

  4, 
  A 
  nephridium 
  from 
  a 
  specimen 
  40 
  mm. 
  long, 
  not 
  yet 
  sexually 
  mature, 
  X 
  20. 
  

  

  Plate 
  35 
  

   Urechis 
  caupo 
  Fisher 
  and 
  MacGinitie 
  

  

  1, 
  Arrangement 
  of 
  intestine 
  and 
  mesenteries 
  in 
  fully 
  expanded 
  sjx'cimen, 
  X 
  ^. 
  

  

  Anterior 
  and 
  posterior 
  portions 
  of 
  body 
  have 
  been 
  omitted 
  and 
  the 
  intestine 
  

   has 
  been 
  spread 
  to 
  right 
  and 
  left 
  to 
  show 
  attachments. 
  Normally 
  these 
  

   lateralmost 
  parts 
  overlie 
  the 
  darker 
  and 
  more 
  mesially 
  located 
  portions. 
  A 
  

   section 
  has 
  been 
  removed 
  from 
  respiratory 
  gut 
  to 
  show 
  attachment 
  of 
  mes- 
  

   enteries. 
  C, 
  crop; 
  C^ 
  stomach; 
  G, 
  gizzard; 
  IIG, 
  respiratory 
  gut; 
  M^, 
  

   mesentery 
  of 
  stomach; 
  NC, 
  nerve 
  cord; 
  Si, 
  siphon; 
  Sil 
  and 
  Si2, 
  anterior 
  and 
  

   posterior 
  end 
  of 
  siphon. 
  

  

  2, 
  Portion 
  of 
  midgut 
  at 
  A' 
  of 
  figure 
  1, 
  showing 
  its 
  highly 
  sacculate 
  structure; 
  

  

  mucosa 
  with 
  fine 
  anastomosing 
  plications, 
  transverse 
  in 
  direction; 
  Si, 
  

   siphon, 
  X 
  2. 
  

  

  3, 
  Postsiphonal 
  midgut 
  at 
  XX 
  of 
  figure 
  1, 
  X 
  2, 
  showing 
  the 
  mucosa 
  and 
  longitudi- 
  

  

  nal 
  muscle 
  band 
  marking 
  position 
  of 
  ciliated 
  groove. 
  

  

  4, 
  4a, 
  Cestode 
  larvae 
  from 
  anterior 
  end 
  of 
  the 
  siphon, 
  X 
  60. 
  These 
  larvae 
  vary 
  

  

  in 
  length 
  from 
  0.25 
  to 
  0.32 
  mm. 
  and 
  are 
  free 
  in 
  the 
  lumen 
  of 
  siphon 
  and 
  in 
  

   the 
  hernialike 
  swellings, 
  which 
  may 
  be 
  caused 
  by 
  them 
  (.see 
  fig. 
  5, 
  above 
  Sil). 
  

  

  5, 
  Sagittal 
  section, 
  X 
  5, 
  of 
  the 
  distal 
  end 
  of 
  stomach 
  and 
  beginning 
  of 
  midgut 
  and 
  

  

  siphon, 
  showing 
  macroscopic 
  character 
  of 
  mucosa; 
  C^, 
  stomach; 
  CG, 
  one 
  side 
  

   only 
  the 
  ciliated 
  groove; 
  the 
  groove 
  is 
  constituted 
  by 
  two 
  of 
  these 
  finely 
  

   plicated 
  folds 
  or 
  ridges 
  of 
  the 
  mucosa. 
  The 
  plications 
  are 
  coarser 
  and 
  the 
  

   groove 
  is 
  broader 
  in 
  the 
  short 
  segment 
  CG'; 
  Si, 
  siphon, 
  showing 
  foliose 
  

   mucosa. 
  The 
  cestode 
  larvae 
  were 
  found 
  in 
  this 
  portion 
  and 
  in 
  the 
  hernia- 
  

   like 
  swellings 
  shown 
  just 
  above 
  SjI, 
  the 
  narrow 
  passage 
  connecting 
  midgut 
  

   and 
  siphon. 
  

  

  6, 
  Fecal 
  pellets, 
  X 
  3. 
  Specinjen 
  from 
  Monterey 
  Bay, 
  Calif. 
  

  

  Plate 
  36 
  

  

  1, 
  I'rrchin 
  chilcnaia 
  (Miillcr): 
  Anterior 
  end 
  of 
  respiratory 
  gut 
  showing 
  mode 
  of 
  

  

  attachment 
  by 
  muscular 
  mesenteries, 
  X 
  3. 
  Compare 
  wit 
  It 
  figures 
  2 
  and 
  3. 
  

  

  2, 
  r'rec/ii« 
  c«i/po 
  Fisher 
  and 
  MacGinitie, 
  X 
  1.5. 
  

  

  3, 
  IJrechis 
  unicinctu8 
  (von 
  Drasche), 
  X 
  5. 
  

  

  4, 
  L'rechin 
  caupo: 
  Cloacal 
  region 
  of 
  a 
  relaxed 
  specimen 
  (pi. 
  35, 
  fig. 
  1) 
  with 
  the 
  

  

  posterior 
  part 
  of 
  respiratory 
  gut 
  ; 
  dorsal 
  wall 
  of 
  cloaca 
  removed. 
  ..1 
  V, 
  anal 
  

   vcHicle; 
  M^, 
  nmscular 
  masentery 
  anchoring 
  the 
  stomach; 
  M*, 
  muscular 
  

   fronula 
  of 
  cloaca; 
  A^, 
  ncphridia; 
  NC, 
  ncrvo 
  cord; 
  PS, 
  posterior 
  setae. 
  

  

  Plate 
  37 
  

  

  Urechis 
  caupo 
  anfl 
  Conmiensals 
  

  

  1, 
  Portion 
  of 
  tunnel 
  showing 
  one 
  position 
  of 
  worm 
  while 
  pumping 
  water 
  through 
  

   its 
  slime-net 
  and 
  characteristic 
  stations 
  of 
  commen.sals, 
  X 
  *i. 
  A, 
  Cleve- 
  

   landia 
  ion 
  (Jordan 
  and 
  Gilbert) 
  at 
  mouth 
  of 
  tube; 
  B, 
  IlespcronoS 
  advrntor 
  

   (Skogsberg) 
  ; 
  C, 
  Scleroplax 
  granulata 
  Rathbun; 
  D, 
  Cnjplomya 
  californica 
  

   (Conrad). 
  At 
  U|)i)er 
  [)f)irit 
  where 
  tube 
  is 
  interrupted 
  one 
  inch 
  has 
  been 
  

   omitted, 
  at 
  lower 
  point 
  four 
  inches. 
  

  

  