﻿238 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.96 
  

  

  lets. 
  Just 
  before 
  the 
  liind-gut 
  passes 
  into 
  the 
  small 
  cloaca 
  there 
  is 
  a 
  

   spherical 
  ventral 
  coecum, 
  to 
  which 
  extends 
  the 
  ventral 
  blood 
  vessel. 
  

  

  The 
  vascular 
  system 
  can 
  be 
  readily 
  followed 
  on 
  plate 
  22. 
  The 
  

   neurointestinal 
  connective 
  forms 
  a 
  loop 
  around 
  the 
  interbasal 
  muscle 
  

   of 
  the 
  setae. 
  The 
  two 
  flaplike 
  expansions 
  of 
  this 
  vessel, 
  shown 
  in 
  

   the 
  figure, 
  are 
  not 
  present 
  in 
  the 
  Tomales 
  Bay 
  specimen. 
  The 
  dorsal 
  

   vessel 
  varies 
  widely 
  in 
  diameter 
  being 
  sometimes 
  greatly 
  inflated 
  

   (Tomales 
  Bay), 
  the 
  inflation 
  extending 
  into 
  the 
  neurointestinal 
  

   connective. 
  

  

  Owing 
  to 
  the 
  very 
  thin, 
  translucent 
  body 
  wall 
  the 
  nerves 
  can 
  some- 
  

   times 
  be 
  seen 
  under 
  strong 
  illumination 
  such 
  as 
  sunlight. 
  They 
  pass 
  

   directly 
  around 
  the 
  body, 
  from 
  the 
  ventral 
  nerve 
  cord, 
  without 
  visible 
  

   branches. 
  The 
  translucent 
  proboscis 
  affords 
  an 
  opportunity 
  to 
  trace 
  

   the 
  proboscis 
  loop 
  throughout 
  its 
  entire 
  course 
  (pi. 
  21, 
  fig. 
  2), 
  This 
  

   ganglionic 
  continuation 
  of 
  the 
  ventral 
  cord 
  is 
  near 
  the 
  margin 
  of 
  the 
  

   proboscis, 
  to 
  which 
  numerous 
  tiny 
  nerves 
  pass 
  from 
  slight 
  ganglionic 
  

   thickenings 
  on 
  the 
  outer 
  side 
  of 
  the 
  cord. 
  No 
  nerves, 
  under 
  favorable 
  

   conditions, 
  could 
  be 
  detected 
  on 
  the 
  mesial 
  side 
  of 
  the 
  cord. 
  

  

  Color 
  in 
  hfe: 
  "Proboscis 
  yellow 
  orange, 
  deepest 
  on 
  edge; 
  body 
  dull 
  

   grey-violet 
  with 
  greenish 
  raised 
  specks 
  about 
  0.5 
  mm. 
  in 
  diameter, 
  

   spaced 
  quite 
  regularly 
  about 
  0.5 
  mm. 
  apart 
  (the 
  papillae); 
  8 
  Ughter 
  

   colored 
  muscle 
  bands" 
  (large 
  specimen 
  from 
  Tomales 
  Bay). 
  

  

  Small 
  phase 
  (figs. 
  12, 
  13; 
  pi. 
  21, 
  figs. 
  4, 
  4a-b). 
  Small 
  examples 
  

   are 
  fairly 
  common 
  on 
  muddy 
  bottom 
  in 
  moderate 
  depths 
  off 
  southern 
  

   CaHfornia 
  and 
  in 
  Newport 
  Bay. 
  These 
  preserve 
  badly 
  unless 
  special 
  

   care 
  is 
  exercised. 
  They 
  are 
  usually 
  strongly 
  contracted 
  into 
  sub- 
  

   spherical 
  form 
  and 
  vary 
  greatly 
  in 
  appearance. 
  Sometimes 
  the 
  body 
  

   wall 
  is 
  rather 
  uniformly 
  transparent 
  but 
  more 
  often 
  the 
  posterior 
  

   portion 
  is 
  opaque. 
  This 
  region 
  may 
  be 
  smooth 
  or 
  thrown 
  into 
  eight 
  

   meridional 
  swellings 
  which 
  occasionally 
  extend 
  the 
  whole 
  length, 
  

   giving 
  the 
  appearance 
  of 
  a 
  tiny 
  melon. 
  These 
  swellings 
  are 
  caused 
  

   by 
  the 
  contraction 
  of 
  the 
  eight 
  muscle 
  bands 
  and 
  are 
  found 
  in 
  strongly 
  

   contracted 
  specimens 
  7 
  mm. 
  long. 
  But 
  specimens 
  in 
  which 
  the 
  body 
  

   wall 
  is 
  stretched 
  and 
  transparent 
  do 
  not 
  show 
  indications 
  of 
  differ- 
  

   entiated 
  muscle 
  bands 
  until 
  much 
  later 
  — 
  at 
  a 
  length 
  of 
  about 
  15 
  to 
  

   20 
  mm. 
  In 
  the 
  very 
  small 
  sizes 
  the 
  muscles 
  are 
  Ukely 
  to 
  show 
  first 
  

   posteriorly 
  and 
  ventrally. 
  A 
  specimen 
  20 
  mm. 
  long 
  from 
  55 
  fathoms 
  

   off 
  Santa 
  Cruz 
  Island 
  has 
  the 
  8 
  bands 
  fully 
  developed. 
  Even 
  in 
  large 
  

   specimens 
  (40 
  mm.) 
  the 
  bands 
  are 
  not 
  always 
  equally 
  conspicuous. 
  

  

  I 
  have 
  found 
  a 
  specimen 
  7 
  mm. 
  long 
  sexually 
  mature. 
  Normally 
  

   these 
  small 
  examples 
  are 
  transparent 
  in 
  the 
  midregion 
  so 
  that 
  the 
  

   nerve 
  cord, 
  intestinal 
  pellets, 
  and 
  egg-laden 
  nephridia 
  can 
  be 
  plainly 
  

   seen 
  as 
  yellowish 
  bodies 
  in 
  life. 
  The 
  intestine 
  is 
  characteristically 
  

   thin-walled, 
  transparent, 
  and 
  highly 
  convoluted 
  and 
  taxes 
  the 
  capacity 
  

   of 
  the 
  body 
  cavity. 
  Its 
  walls 
  are 
  greatly 
  distended 
  with 
  mud 
  peUets 
  

  

  