﻿AUG 
  1? 
  IW 
  

  

  ON 
  THE 
  BRANCHIAL 
  VESSliLS 
  OF 
  STERNASPIS, 
  

  

  On 
  the 
  Branchial 
  Vessels 
  of 
  Sternaspis. 
  

  

  By 
  

  

  l^clwin 
  8. 
  Ooo<li'icli, 
  TII.A., 
  

  

  Fellow 
  of 
  Merton 
  College, 
  Oxford. 
  

  

  WiUi 
  Plates 
  1 
  and 
  2. 
  

  

  Some 
  years 
  ngo, 
  when 
  stud_ying- 
  the 
  interesting* 
  worm 
  

   Sternaspis 
  til 
  a 
  lassemo 
  ides, 
  Otto, 
  at 
  the 
  Zoological 
  Station 
  

   at 
  Naples, 
  for 
  the 
  purpose 
  of 
  describing 
  the 
  strnctni'e 
  of 
  its 
  

   excretory 
  and 
  reproductive 
  organs 
  (2), 
  I 
  examined 
  the 
  very 
  

   remarkable 
  and 
  beautiful 
  vascular 
  apparatus 
  whicli 
  supplies 
  

   the 
  gill 
  filaments 
  at 
  the 
  hind 
  end 
  of 
  the 
  body. 
  Finding 
  that 
  

   the 
  branchial 
  organs 
  of 
  Sternaspis 
  did 
  not 
  appear 
  to 
  agree 
  in 
  

   the 
  details 
  of 
  their 
  organisation 
  with 
  any 
  of 
  the 
  descriptions 
  

   hitherto 
  given, 
  I 
  determined 
  to 
  work 
  ont 
  their 
  minute 
  ana- 
  

   tomy. 
  But 
  owing 
  to 
  their 
  very 
  small 
  size, 
  to 
  the 
  presence 
  of 
  

   a 
  tough 
  cuticle, 
  and 
  to 
  an 
  external 
  layer 
  of 
  sandy 
  particles, 
  it 
  

   is 
  very 
  difficult 
  indeed 
  to 
  make 
  out 
  the 
  exact 
  relation 
  of 
  the 
  

   various 
  blood-vessels 
  to 
  the 
  gill 
  filauients, 
  either 
  by 
  dissection 
  

   or 
  by 
  serial 
  sections. 
  It 
  is, 
  therefore, 
  only 
  after 
  repeated 
  

   failures, 
  that 
  it 
  is 
  at 
  last 
  possible 
  for 
  me 
  to 
  present 
  what 
  is, 
  I 
  

   believe, 
  a 
  correct 
  account 
  of 
  their 
  structure. 
  

  

  Max 
  Miillei- 
  mentioned 
  the 
  dorsal 
  branchial 
  vessels 
  of 
  

   Sternaspis 
  in 
  1852, 
  and 
  some 
  years 
  later 
  Claparede 
  figured 
  

   them 
  and 
  briefly 
  described 
  them. 
  Each 
  blood-vessel, 
  accord- 
  

   ing 
  to 
  Claparede, 
  is 
  '^ 
  accole 
  a 
  uii 
  axe 
  solide, 
  elastique 
  et 
  

  

  cylindrique 
  de 
  consistance 
  cartilagineuse," 
  which 
  is 
  

  

  said 
  to 
  be 
  surrounded 
  by 
  a"serie 
  d'anneaux 
  musculaires" 
  (2). 
  

  

  The 
  first 
  detailed 
  account 
  of 
  the 
  blood-supply 
  of 
  the 
  gills 
  is 
  

   given 
  in 
  Vejdovsky's 
  great 
  memoir 
  (5). 
  He 
  describes 
  two 
  

   bundles 
  of 
  " 
  branchial 
  arteries 
  " 
  springing 
  from 
  the 
  dorsal 
  

  

  VOL. 
  48, 
  PAUT 
  1 
  NEW 
  SERIES, 
  1 
  

  

  