﻿268 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.96 
  

  

  present, 
  and 
  numerous 
  somewhat 
  variable 
  muscles 
  radiate 
  from 
  the 
  

   coelomic 
  end. 
  Inside 
  the 
  seta 
  sac 
  a 
  short 
  substitute 
  seta 
  is 
  often 
  

   present 
  close 
  beside 
  the 
  functional 
  one. 
  

  

  Anal 
  setae 
  curved 
  terminally, 
  sharp, 
  10 
  or 
  11 
  in 
  number, 
  and 
  the 
  

   dorsal 
  are 
  longer 
  (8.5 
  mm.) 
  than 
  the 
  ventral 
  (7.3 
  mm.). 
  The 
  dorsal 
  

   are 
  the 
  only 
  ones 
  used 
  to 
  any 
  extent 
  in 
  cleaning 
  out 
  the 
  burrow. 
  

   When 
  digging, 
  the 
  posterior 
  end 
  of 
  the 
  body 
  is 
  bent 
  sharply 
  forward, 
  

   underneath, 
  so 
  that 
  the 
  ventral 
  setae 
  touch 
  the 
  ventral 
  surface 
  of 
  the 
  

   worm, 
  while 
  the 
  strongly 
  exserted 
  dorsal 
  bristles 
  scrape 
  the 
  mud 
  

   backward 
  as 
  the 
  body 
  is 
  again 
  straightened. 
  This 
  habit 
  helps 
  to 
  

   explain 
  the 
  absence 
  of 
  a 
  midventral 
  seta, 
  there 
  being 
  a 
  broader 
  gap 
  

   at 
  that 
  point. 
  The 
  anus 
  is 
  eccentric 
  to 
  the 
  circle 
  of 
  setae, 
  being 
  

   nearer 
  to 
  the 
  ventral 
  side 
  (center 
  of 
  anus 
  6 
  or 
  6.5 
  mm. 
  from 
  dorsal 
  

   setae 
  and 
  4 
  or 
  4.5 
  mm. 
  from 
  the 
  ventral). 
  All 
  bristles 
  show 
  conspic- 
  

   uous 
  cross-banding. 
  

  

  There 
  are 
  three 
  pairs 
  of 
  nephridia 
  varying 
  greatly 
  in 
  size 
  according 
  

   to 
  degree 
  of 
  distension 
  with 
  eggs 
  or 
  sperm. 
  In 
  one 
  specimen 
  ex- 
  

   amined 
  the 
  posterior 
  tubes 
  were 
  150 
  mm. 
  long 
  and 
  10 
  mm. 
  in 
  diam- 
  

   eter, 
  reaching 
  two-thirds 
  the 
  total 
  length 
  of 
  animal. 
  The 
  anterior 
  

   pair 
  is 
  situated 
  close 
  to 
  the 
  setae. 
  Rarely, 
  one 
  nephridium 
  of 
  this 
  

   pair 
  is 
  missing. 
  The 
  nephrostome 
  is 
  on 
  the 
  anterior 
  side 
  at 
  the 
  base 
  

   and 
  the 
  grooved 
  ciliated 
  lips 
  are 
  very 
  long 
  and 
  spirally 
  coiled. 
  Mac- 
  

   Ginitie 
  (1935a) 
  has 
  shown 
  that 
  the 
  superficial 
  groove, 
  V-shape 
  in 
  sec- 
  

   tion 
  in 
  the 
  male 
  and 
  more 
  C-shape 
  in 
  the 
  female, 
  communicates 
  by 
  

   a 
  slit 
  along 
  its 
  bottom 
  with 
  what 
  is 
  virtually 
  an 
  almost 
  closed 
  duct 
  

   or 
  tube 
  underneath. 
  In 
  both 
  upper 
  and 
  deeper 
  parts 
  of 
  groove 
  the 
  

   cilia 
  beat 
  toward 
  the 
  nephridium 
  while 
  on 
  the 
  outside 
  of 
  the 
  lips, 
  

   bordering 
  the 
  superficial 
  groove, 
  they 
  carry 
  materials 
  in 
  the 
  opposite 
  

   direction 
  and 
  incidentally 
  help 
  in 
  the 
  circulation 
  of 
  the 
  coelomic 
  

   fluid 
  and 
  contained 
  blood 
  cells. 
  "As 
  the 
  eggs, 
  blood 
  cells, 
  and 
  other 
  

   coelomic 
  materials 
  pass 
  along 
  the 
  outside 
  of 
  the 
  thread 
  the 
  eggs 
  are 
  

   caught 
  in 
  the 
  external 
  portion 
  of 
  the 
  groove, 
  are 
  fed 
  into 
  the 
  inner 
  

   channel 
  and 
  then 
  proceed 
  to 
  the 
  opening 
  leading 
  into 
  the 
  storage 
  

   reservoir 
  [nephridium]. 
  They 
  are 
  carried 
  toward 
  the 
  reservoir 
  at 
  the 
  

   approximate 
  rate 
  of 
  7 
  spirals 
  per 
  minute. 
  Thus 
  the 
  eggs 
  are 
  sepa- 
  

   rated 
  from 
  all 
  other 
  coelomic 
  materials. 
  As 
  the 
  eggs 
  pass 
  through 
  

   the 
  slit 
  between 
  the 
  external 
  portion 
  of 
  the 
  groove 
  to 
  the 
  inner 
  chan- 
  

   nel, 
  they 
  are 
  under 
  considerable 
  pressure. 
  They 
  enter 
  as 
  a 
  wedge, 
  

   then 
  become 
  disc-shaped 
  in 
  the 
  slit, 
  and 
  finally 
  round 
  out 
  in 
  the 
  in- 
  

   ner 
  channel. 
  Only 
  mature 
  eggs 
  with 
  indentations 
  are 
  collected 
  in 
  

   this 
  way. 
  As 
  the 
  eggs 
  pass 
  along 
  the 
  inner 
  groove 
  toward 
  the 
  storage 
  

   organ 
  they 
  become 
  oriented 
  with 
  the 
  convex 
  surface 
  of 
  one 
  egg 
  

   pushed 
  into 
  the 
  indentation 
  of 
  the 
  egg 
  ahead, 
  thus 
  forming 
  a 
  com- 
  

   pact 
  chain. 
  Blood 
  cells 
  (which 
  range 
  from 
  0.014 
  to 
  0.02 
  mm. 
  in 
  di- 
  

   ameter) 
  and 
  immature 
  egg 
  cells 
  pass 
  along 
  the 
  collecting 
  threads 
  (i. 
  e., 
  

  

  