﻿FOURTH 
  REPORT 
  OF 
  THE 
  DIRECTOR 
  KJO/ 
  

  

  161 
  

  

  former 
  was 
  internal. 
  These 
  are 
  silicious 
  sponges 
  allied 
  to 
  Euplec- 
  

   tella 
  and 
  though 
  we 
  find 
  no 
  parallel 
  expression 
  of 
  commensalism 
  

   in 
  the 
  living 
  glass 
  sponges, 
  yet 
  Euplectella 
  carries 
  a 
  parasite 
  in 
  the 
  

   form 
  of 
  a 
  crustacean 
  which 
  in 
  youth 
  enters 
  its 
  open 
  cloacal 
  cavity 
  

   and 
  remains 
  there 
  so 
  that 
  when 
  the 
  sponge 
  has 
  in 
  adult 
  growth 
  

   built 
  the 
  terminal 
  or 
  sieveplate 
  over 
  its 
  aperture 
  the 
  crustacean 
  is 
  

   wholly 
  and 
  permanently 
  caged. 
  

  

  A 
  very 
  commanding 
  illustration 
  of 
  the 
  association 
  between 
  the 
  

   sponges 
  and 
  spiral 
  annelids 
  is 
  afforded 
  by 
  a 
  series 
  of 
  specimens 
  

   displayed 
  in 
  the 
  British 
  Museum. 
  These 
  I 
  am 
  able 
  to 
  re- 
  

   produce 
  here 
  by 
  the 
  kindness 
  of 
  the 
  trustees 
  of 
  that 
  Museum 
  from 
  

   photographs 
  made 
  by 
  permission 
  of 
  the 
  Keeper 
  of 
  the 
  Depart- 
  

   ment 
  of 
  Geology, 
  through 
  the 
  friendly 
  agency 
  of 
  Dr 
  F. 
  A. 
  Bather. 
  In 
  

   all 
  these 
  specimens 
  it 
  would 
  appear 
  that 
  the 
  worm, 
  which 
  has 
  made 
  

   a 
  tube 
  of 
  large 
  dimensions, 
  began 
  its 
  commensal 
  existence 
  early 
  in 
  

   the 
  life 
  of 
  the 
  sponge 
  and 
  has 
  coiled 
  upward 
  in 
  a 
  very 
  loose 
  spiral 
  

   about 
  and 
  just 
  within 
  the 
  cloacal 
  wall. 
  Of 
  the 
  figures 
  given 
  here 
  two 
  

  

  These 
  and 
  the 
  figure 
  on 
  the 
  preceding 
  page 
  represent 
  silicified 
  sponges 
  with 
  spiral 
  annelid 
  

   tubes 
  from 
  the 
  English 
  Chalk. 
  In 
  the 
  upper 
  figure 
  (locality 
  unknown) 
  and 
  the 
  lower 
  right- 
  

   hand 
  figure 
  ( 
  Beckhampton 
  ), 
  the 
  exposed 
  worm 
  tube 
  is 
  coiled 
  about 
  a 
  vertical 
  tube 
  which 
  

   appears 
  to 
  be 
  the 
  silicified 
  wall 
  of 
  the 
  cloaca. 
  These 
  spirals 
  are 
  obviously 
  in 
  reversed 
  direc- 
  

   tion. 
  The 
  lower 
  left-hand 
  figure 
  is 
  a 
  direct 
  print 
  from 
  a 
  thin 
  section 
  of 
  another 
  sponge 
  in 
  

   which 
  the 
  position 
  of 
  the 
  worm 
  tube, 
  cloaca 
  and 
  concentric 
  structure 
  of 
  the 
  sponge 
  are 
  

   shown. 
  Prepared 
  by 
  Dr. 
  Bather. 
  Figures 
  about 
  natural 
  size. 
  British 
  Museum 
  (Natural 
  

   History) 
  Department 
  of 
  Geology: 
  A. 
  4751 
  5S"7 
  

  

  