﻿418 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  

  

  The 
  two 
  large, 
  ventral 
  retractors 
  (fig. 
  13) 
  have 
  their 
  origin 
  m 
  wide 
  

   attachments 
  at 
  the 
  posterior 
  end 
  of 
  the 
  middle 
  thkd 
  of 
  the 
  length 
  of 
  

   the 
  trmik. 
  The 
  pair 
  of 
  nephridia 
  are 
  very 
  long, 
  and 
  attached 
  to 
  the 
  

   body 
  wall 
  slightly 
  behind 
  the 
  anus. 
  The 
  esophagus 
  is 
  slender, 
  and 
  the 
  

   large 
  coil 
  of 
  the 
  intestine 
  nearly 
  fills 
  the 
  posterior 
  part 
  of 
  the 
  cavity 
  

   of 
  the 
  trunk. 
  A 
  spindle 
  muscle 
  is 
  inserted 
  in 
  the 
  body 
  wall 
  immedi- 
  

   ately 
  behind 
  the 
  anus, 
  and 
  muscle 
  strands 
  run 
  from 
  the 
  intestinal 
  coil 
  

   to 
  each 
  side 
  of 
  the 
  wall 
  of 
  the 
  body 
  slightly 
  in 
  front 
  of 
  the 
  origin 
  of 
  the 
  

   retractor 
  muscles. 
  The 
  esophagus 
  bears 
  upon 
  the 
  dorsal 
  surface 
  at 
  its 
  

  

  Fig. 
  13.— 
  Dissection 
  of 
  Dendkostoma 
  alutaceum. 
  x 
  lOf. 
  

   PoLiA» 
  tubule. 
  

  

  an, 
  anus; 
  nepJi, 
  nephridium; 
  tb.Pol, 
  

  

  posterior 
  end 
  an 
  enlargement 
  of 
  the 
  Polian 
  canal 
  in 
  the 
  form 
  of 
  a 
  small 
  

   sac 
  (fig. 
  13), 
  from 
  which 
  a 
  bunch 
  of 
  fine 
  blind 
  tubes 
  run 
  backward 
  into 
  

   the 
  intestinal 
  coil, 
  and 
  isolated 
  tubes 
  extend 
  to 
  the 
  ventral 
  side 
  of 
  the 
  

   body 
  wall. 
  These 
  tubes 
  when 
  stretched 
  become 
  straight, 
  but, 
  when 
  

   the 
  tension 
  is 
  relaxed, 
  they 
  take 
  the 
  form 
  of 
  a 
  fine 
  spiral. 
  Varicosities 
  

   occur 
  at 
  intervals 
  in 
  the 
  larger 
  tubules. 
  Two 
  faintly 
  pigmented 
  eye 
  

   spots 
  are 
  visible 
  in 
  one 
  of 
  the 
  larger 
  specimens. 
  The 
  cerebral 
  ganglion 
  

   as 
  seen 
  from 
  above 
  with 
  a 
  low 
  power 
  has 
  nearly 
  a 
  circular 
  contour; 
  a 
  

   prominent, 
  crescentic 
  cerebral 
  organ 
  extends 
  in 
  front 
  of 
  it. 
  No 
  

   nuchal 
  organ 
  was 
  observed. 
  

  

  