﻿456 
  On 
  the 
  Structure 
  o/" 
  Magelona. 
  

  

  considered 
  to 
  belong 
  to 
  the 
  genus 
  Magelona, 
  Fritz 
  Midler, 
  

   at 
  St. 
  Vaast 
  la 
  Hougue. 
  In 
  its 
  youngest 
  condition 
  it 
  presents 
  

   a 
  somewhat 
  club-shaped 
  appearance 
  — 
  broad 
  in 
  front 
  and 
  

   rather 
  narrowed 
  posteriorly. 
  The 
  anterior 
  end 
  has 
  an 
  open 
  

   ciliated 
  funnel, 
  then 
  follows 
  about 
  twenty 
  segments, 
  each 
  

   with 
  a 
  ciliated 
  ring, 
  while 
  posteriorly 
  the 
  abruptly 
  truncated 
  

   tail 
  has 
  a 
  ring 
  of 
  long 
  cilia 
  round 
  the 
  anus. 
  In 
  addition 
  to 
  

   the 
  cilia 
  on 
  the 
  funnel 
  the 
  anterior 
  end 
  bears 
  a 
  tuft 
  at 
  each 
  

   side 
  (doubtless 
  homologous 
  with 
  the 
  lateral 
  cephalic 
  pencil 
  

   in 
  the 
  Nemerteans), 
  besides 
  a 
  papilla 
  armed 
  with 
  a 
  tuft 
  of 
  

   bristles 
  nearly 
  as 
  long 
  as 
  the 
  body, 
  after 
  the 
  manner 
  of 
  the 
  

   young 
  Polydora. 
  The 
  alimentary 
  caual 
  proceeds 
  straight 
  

   from 
  mouth 
  to 
  anus. 
  The 
  next 
  stage 
  shows 
  a 
  heart-shaped 
  

   snout 
  with 
  four 
  eyes, 
  and 
  at 
  the 
  base 
  between 
  it 
  and 
  the 
  

   body-collar 
  a 
  pair 
  of 
  short 
  tentacles 
  with 
  brown 
  bars 
  (which 
  

   differ 
  quite 
  from 
  the 
  dark 
  pigment-bars 
  of 
  the 
  tentacles 
  in 
  

   Magelona) 
  on 
  the 
  anterior 
  border 
  near 
  the 
  tip, 
  and 
  a 
  series 
  

   of 
  palpocils 
  ; 
  while 
  internally 
  is 
  a 
  cavity 
  containing 
  a 
  csecal 
  

   blood-vessel 
  (according 
  to 
  the 
  type 
  M. 
  Claparede 
  states 
  he 
  

   usually 
  found 
  in 
  the 
  Spionidae), 
  with 
  corpusculated 
  blood. 
  

   The 
  first 
  body-segment 
  still 
  bears 
  at 
  each 
  side 
  the 
  tuft 
  of 
  

   long 
  larval 
  bristles, 
  and 
  is 
  succeeded 
  by 
  eight 
  distinct 
  bristle- 
  

   bundles. 
  The 
  ninth 
  segment 
  carries 
  a 
  row 
  of 
  hooks 
  on 
  each 
  

   side. 
  A 
  simple 
  pyriform 
  anal 
  papilla 
  terminates 
  the 
  body. 
  

   The 
  alimentary 
  canal 
  is 
  differentiated 
  anteriorly 
  into 
  a 
  

   muscular 
  oesophagus, 
  and 
  the 
  mouth 
  closely 
  approaches 
  that 
  

   of 
  Magelona. 
  Behind 
  the 
  oesophagus 
  the 
  canal 
  exhibits 
  two 
  

   short 
  glandular 
  diverticula 
  and 
  then 
  proceeds 
  in 
  the 
  usual 
  

   moniliform 
  manner 
  to 
  the 
  anus. 
  The 
  body 
  is 
  tinted 
  with 
  

   various 
  brownish 
  transverse 
  bands. 
  In 
  this 
  condition 
  the 
  

   flattened 
  spatulate 
  snout 
  has 
  a 
  considerable 
  resemblance 
  to 
  

   that 
  in 
  Magelona, 
  but 
  the 
  subsequent 
  stage 
  shows 
  less 
  

   affinity, 
  for 
  the 
  long 
  tentacles 
  have 
  slender 
  palpocils, 
  which 
  

   differ 
  in 
  character 
  and 
  arrangement 
  from 
  those 
  in 
  the 
  British 
  

   form. 
  Moreover, 
  the 
  cephalic 
  region 
  has 
  greatly 
  diminished, 
  

   its 
  shape 
  being 
  that 
  of 
  a 
  short 
  truncated 
  cone, 
  with 
  four 
  eyes 
  

   arranged 
  in 
  a 
  transverse 
  manner 
  at 
  the 
  base. 
  The 
  first 
  

   segment 
  of 
  the 
  body 
  retains 
  the 
  long 
  larval 
  bristles, 
  but 
  the 
  

   succeeding 
  segments 
  to 
  the 
  eighth 
  have 
  lost 
  their 
  shorter 
  

   temporary 
  bristles. 
  From 
  the 
  ninth 
  segment 
  backward, 
  

   however, 
  four 
  or 
  five 
  pairs 
  of 
  longer 
  and 
  stronger 
  bristles 
  

   occur, 
  in 
  association 
  with 
  the 
  rows 
  of 
  hooks 
  (which 
  conform 
  

   in 
  structure 
  to 
  the 
  Spio 
  type). 
  The 
  blood 
  is 
  bluish. 
  The 
  

   posterior 
  end 
  has 
  the 
  form 
  of 
  a 
  peculiar 
  hoof-shaped 
  process 
  

   furnished 
  with 
  small 
  papillae. 
  

  

  The 
  fragmentary 
  state, 
  therefore, 
  in 
  which 
  our 
  knowledge 
  

  

  