﻿MARINE 
  POLYCHAETE 
  WORMS 
  — 
  PETTIBONE 
  245 
  

  

  unmodified 
  setigers 
  and 
  a 
  well-developed 
  posterior 
  region; 
  there 
  is 
  a 
  

   single 
  achaetous 
  tentacular 
  segment 
  with 
  two 
  pairs 
  of 
  tentacular 
  cirri; 
  

   the 
  first 
  setigerous 
  segment 
  in 
  the 
  female 
  is 
  similar 
  to 
  the 
  following 
  

   segment, 
  but 
  in 
  the 
  male 
  it 
  has 
  a 
  very 
  long 
  pair 
  of 
  dorsal 
  cirri 
  similar 
  

   to 
  the 
  median 
  antenna. 
  Thus 
  the 
  male 
  stolons 
  of 
  the 
  different 
  species 
  

   of 
  Autolytus 
  agree 
  in 
  having 
  a 
  very 
  long 
  pair 
  of 
  anterior 
  cirri 
  similar 
  

   to 
  the 
  median 
  antenna, 
  but 
  they 
  may 
  be 
  developed 
  as 
  the 
  upper 
  pair 
  

   of 
  tentacular 
  cirri 
  of 
  a 
  single 
  tentacular 
  segment 
  as 
  in 
  ^. 
  prolifer, 
  as 
  

   the 
  dorsal 
  cirri 
  of 
  the 
  first 
  setigerous 
  segment 
  as 
  in 
  ^. 
  alexandri, 
  or 
  as 
  

   the 
  third 
  pair 
  of 
  tentacular 
  cirri 
  on 
  the 
  second 
  tentacular 
  segment 
  

   just 
  dorsal 
  to 
  a 
  pair 
  of 
  achaetous 
  lobes 
  as 
  in 
  A. 
  prismaticus. 
  

  

  The 
  number 
  of 
  setigers 
  in 
  the 
  anterior, 
  unmodified 
  region 
  of 
  the 
  

   sexual 
  stolons 
  appears 
  to 
  be 
  a 
  good 
  taxonomic 
  character 
  for 
  most 
  

   species. 
  That 
  the 
  number 
  is 
  somewhat 
  variable 
  in 
  A. 
  prolifer 
  (usually 
  

   three, 
  sometimes 
  two 
  and 
  four) 
  does 
  not 
  mean 
  that 
  it 
  is 
  of 
  no 
  signifi- 
  

   cance 
  in 
  other 
  forms. 
  Thus 
  the 
  specimens 
  of 
  Autolytus 
  with 
  six 
  

   anterior 
  unmodified 
  setigers, 
  which 
  Dales 
  (1951) 
  referred 
  to 
  A. 
  prolifer, 
  

   are 
  no 
  doubt 
  another 
  species. 
  The 
  description 
  agrees 
  well 
  with 
  that 
  

   of 
  A. 
  cornutus. 
  

  

  All 
  three 
  species 
  of 
  Autolytus 
  from 
  Point 
  Barrow 
  have 
  the 
  body 
  

   linear 
  elongate, 
  attenuated 
  posteriorly, 
  flattened 
  ventrally, 
  arched 
  

   dorsally. 
  Prostomium 
  with 
  four 
  eyes 
  in 
  trapezoidal 
  arrangement, 
  

   with 
  palps 
  fused, 
  turned 
  ventrally, 
  exceeding 
  the 
  prostomium 
  only 
  

   sUghtly. 
  Neuropodia 
  with 
  composite 
  setae 
  with 
  blades 
  short, 
  biden- 
  

   tate, 
  and 
  usually 
  with 
  a 
  simple 
  bayonette 
  seta. 
  

  

  Key 
  to 
  the 
  species 
  of 
  Autolytus 
  from 
  Point 
  Barrow 
  

  

  1. 
  Stem 
  Form: 
  Dorsal 
  cirri 
  irregular 
  in 
  length, 
  at 
  least 
  some 
  longer 
  than 
  body 
  

   width, 
  pigmented 
  with 
  reddish 
  globules; 
  body 
  whitish, 
  brownish, 
  or 
  trans- 
  

   versely 
  banded 
  with 
  reddish 
  globules, 
  2 
  narrow 
  bands 
  per 
  segment; 
  with 
  

   nuchal 
  epaulettes 
  on 
  first 
  2 
  (to 
  4) 
  setigers; 
  sexual 
  buds 
  formed 
  singly 
  (?), 
  

   the 
  heads 
  forming 
  posterior 
  to 
  setiger 
  14. 
  Sexual 
  Stolons: 
  14 
  setigers 
  

   anterior 
  to 
  swimming 
  setae; 
  nuchal 
  epaulettes 
  on 
  first 
  3 
  setigers; 
  2 
  pairs 
  

   tentacular 
  cirri, 
  the 
  upper 
  one 
  longer; 
  in 
  male, 
  first 
  pair 
  dorsal 
  cirri 
  on 
  first 
  

   setiger 
  very 
  long, 
  similar 
  to 
  median 
  antenna; 
  female 
  stolons 
  with 
  2-lobed 
  

  

  egg 
  sac 
  A. 
  alexandri 
  

  

  Stem 
  Form: 
  Dorsal 
  cirri, 
  except 
  anterior 
  2 
  pairs, 
  shorter 
  than 
  body 
  width, 
  

   not 
  extending 
  beyond 
  or 
  only 
  slightly 
  be3'ond 
  the 
  setae, 
  subequal; 
  sexual 
  

   buds 
  formed 
  singly, 
  the 
  heads 
  forming 
  between 
  setigers 
  13 
  and 
  14. 
  Sexual 
  

   Stolons: 
  6 
  setigers 
  anterior 
  to 
  swimming 
  setae; 
  3 
  pairs 
  tentacular 
  cirri; 
  in 
  

   male, 
  first 
  pair 
  similar 
  to 
  dorsal 
  cirri, 
  with 
  second 
  short 
  pair 
  at 
  its 
  ventral 
  

   base, 
  third 
  pair 
  very 
  long 
  and 
  stout 
  (similar 
  to 
  median 
  antenna) 
  with 
  small 
  

   achaetous 
  lobe 
  at 
  its 
  ventral 
  base 
  (fig. 
  29, 
  e, 
  f) 
  ; 
  in 
  the 
  female, 
  similar 
  except 
  

   both 
  the 
  first 
  and 
  third 
  pairs 
  are 
  similar 
  to 
  the 
  following 
  dorsal 
  cirri 
  (fig. 
  

   29, 
  c, 
  d); 
  female 
  stolons 
  with 
  1-lobed 
  egg 
  sac 
  2 
  

  

  