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  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  

  

  more 
  caeca 
  are 
  found 
  on 
  the 
  rectum. 
  Eggs 
  spherical. 
  The 
  proto- 
  

   troch 
  cells 
  of 
  the 
  embryo 
  form 
  an 
  embryonal 
  envelope, 
  which 
  is 
  cast 
  

   off 
  with 
  the 
  vitellin 
  membrane 
  (S. 
  nudus) 
  . 
  

  

  SIPUNCULUS 
  NUDUS 
  Linnaeus. 
  

  

  This 
  cosmopolitan 
  species 
  occurs 
  in 
  the 
  Mediterranean 
  Sea, 
  on 
  the 
  

   Atlantic 
  coast 
  of 
  Spain 
  and 
  of 
  France, 
  the 
  North 
  Sea, 
  Panama 
  

   (Keferstein, 
  1866), 
  the 
  southern 
  coast 
  of 
  the 
  United 
  States, 
  and 
  also 
  

   the 
  coast 
  of 
  Malacca 
  (Selenka, 
  1883) 
  and 
  Loyalty 
  Islands 
  (Shipley, 
  

   1899). 
  

  

  A 
  specimen 
  of 
  this 
  species 
  from 
  Key 
  West, 
  Florida, 
  and 
  others 
  

   from 
  Beaufort, 
  North 
  Carolina, 
  resemble 
  closely 
  those 
  from 
  the 
  

   English 
  C'hannel 
  (RoscofT, 
  Finist&re), 
  with 
  which 
  I 
  have 
  compared 
  

   them. 
  Another 
  specimen 
  from 
  Key 
  West, 
  probably 
  of 
  this 
  species, 
  

   shows 
  some 
  of 
  the 
  peculiarities 
  ascribed 
  to 
  S. 
  tituhans 
  Selenka 
  and 
  

   Billow. 
  That 
  is, 
  its 
  neplu-idia 
  are 
  attached 
  for 
  nearly 
  one-half 
  their 
  

   length, 
  whereas 
  in 
  specimens 
  of 
  S. 
  nudus 
  (from 
  Roscoff) 
  they 
  are 
  

   attached 
  for 
  one-fourth 
  to 
  one-fifth 
  their 
  length 
  (as 
  in 
  the 
  other 
  

   specimen 
  from 
  Key 
  West 
  that 
  I 
  have 
  examined), 
  and 
  are 
  described 
  

   by 
  Selenka 
  (1883) 
  as 
  free. 
  The 
  specimen 
  appears 
  to 
  be 
  pigmented 
  

   also, 
  though 
  how 
  much 
  of 
  its 
  present 
  hue 
  may 
  be 
  due 
  to 
  discolora- 
  

   tion 
  through 
  desiccation 
  can 
  not 
  be 
  determined. 
  Otherwise 
  it 
  is 
  a 
  

   typical 
  S. 
  nudus 
  with 
  31-32 
  longitudinal 
  muscle 
  bands, 
  ventral 
  

   retractors 
  arising 
  from 
  longitudinal 
  muscles 
  2-6, 
  dorsal 
  retractors 
  

   from 
  7-11. 
  A 
  specimen 
  from 
  Beaufort, 
  North 
  Carolina, 
  likewise 
  has 
  

   its 
  nephridia 
  attached 
  for 
  two-fifths 
  of 
  their 
  length, 
  though 
  it 
  is 
  not 
  

   different 
  otherwise 
  from 
  S. 
  nudus 
  horn 
  the 
  English 
  Channel. 
  Inas- 
  

   much 
  as 
  the 
  length 
  of 
  the 
  nephridia 
  varies 
  enormously 
  in 
  the 
  living 
  

   animal 
  according 
  to 
  conditions 
  of 
  expansion 
  or 
  contraction, 
  undue 
  

   weight 
  has 
  probably 
  been 
  placed 
  upon 
  this 
  point 
  by 
  Selenka 
  in 
  the 
  

   determination 
  of 
  species. 
  

  

  SIPUNCULUS 
  TITUBANS 
  Selenka 
  and 
  Billow. 
  

  

  Although 
  the 
  scope 
  of 
  this 
  paper 
  does 
  not 
  include 
  the 
  description 
  

   of 
  West 
  Indian 
  sipunculids 
  not 
  also 
  found 
  off 
  the 
  coast 
  of 
  the 
  United 
  

   States, 
  it 
  may 
  be 
  weU 
  to 
  call 
  attention 
  to 
  certain 
  specimens 
  in 
  the 
  

   National 
  Museum 
  from 
  this 
  region 
  which 
  are 
  probably 
  to 
  be 
  identi- 
  

   fied 
  as 
  S. 
  tituhans 
  Selenka 
  and 
  Billow, 
  but 
  which 
  suggest 
  that 
  this 
  

   species 
  may 
  be 
  only 
  a 
  local 
  variety 
  of 
  S. 
  nudus 
  with 
  no 
  very 
  con- 
  

   stantly 
  correlated 
  variations 
  from 
  the 
  widespread 
  form. 
  

  

  Thus 
  a 
  specimen 
  from 
  Jamaica 
  has 
  the 
  nephridia 
  attached 
  through 
  

   half 
  their 
  length 
  as 
  in 
  S. 
  tituhans, 
  but 
  has 
  30 
  longitudinal 
  muscle 
  

   bands 
  as 
  in 
  S. 
  nudus, 
  not 
  26 
  or 
  27 
  as 
  in 
  S. 
  tituhans 
  \' 
  specimens 
  from 
  

   Trinidad 
  have 
  27-28 
  longitudinal 
  muscles, 
  an 
  intermediate 
  condition 
  

  

  » 
  Selenka 
  'and 
  BOlow's 
  original 
  description 
  of 
  S. 
  titubans 
  says 
  2(5; 
  Fischer's 
  26 
  or 
  27 
  in 
  front, 
  32 
  behind. 
  

  

  