﻿36 
  A 
  MONOGRAPPI 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  uppermost 
  part 
  of 
  tlie 
  sponge, 
  in 
  fact, 
  is 
  still 
  in 
  the 
  condition 
  of 
  a 
  simple 
  Ascon- 
  

   person, 
  with 
  an 
  uniisually 
  wide 
  gastral 
  cavity, 
  whose 
  thin 
  walls 
  (about 
  0-025 
  mm. 
  

   thick) 
  exhibit 
  the 
  usual 
  structure, 
  being 
  lined 
  by 
  a 
  layer 
  of 
  collared 
  cells 
  on 
  the 
  inside, 
  

   and 
  perforated 
  by 
  numerous 
  inhalant 
  pores 
  (prosopyles). 
  

  

  At 
  a 
  short 
  distance 
  below 
  the 
  osculum, 
  however, 
  small, 
  hollow 
  buds 
  make 
  their 
  

   appearance 
  as 
  outgrowths 
  of 
  tlie 
  thin 
  tube-wall. 
  These 
  buds 
  are 
  at 
  first 
  simple 
  and 
  

   unbranched. 
  As 
  they 
  grow 
  older 
  they 
  elongate 
  and 
  branch 
  freely 
  towards 
  their 
  distal 
  

   ends, 
  which 
  terminate 
  blindly; 
  this 
  condition 
  prevails 
  lower 
  down 
  in 
  the 
  colony. 
  

   The 
  branches 
  of 
  these 
  numerous 
  radial 
  tubes 
  lie 
  close 
  to 
  one 
  another, 
  frequently 
  

   touching, 
  and 
  form 
  all 
  together 
  the 
  thick 
  wall 
  of 
  the 
  sponge, 
  which, 
  of 
  course, 
  

   gradually 
  increases 
  in 
  thickness 
  as 
  the 
  colony 
  grows 
  older 
  and 
  is 
  hence 
  much 
  thicker 
  

   in 
  the 
  lower 
  than 
  in 
  the 
  upper 
  portion 
  of 
  the 
  sponge. 
  Occasionally 
  the 
  cavities 
  of 
  

   the 
  radial 
  tubes 
  communicate 
  directly 
  one 
  with 
  another 
  but 
  this 
  does 
  not 
  seem 
  to 
  be 
  

   at 
  all 
  general 
  ; 
  an 
  instance 
  is 
  shown 
  in 
  Figure 
  4, 
  Plate 
  V. 
  As 
  they 
  branch 
  towards 
  

   their 
  distal 
  extremities 
  the 
  radial 
  tubes 
  become 
  gradually 
  narrower 
  (PI. 
  V., 
  Fig. 
  4) 
  

   and 
  their 
  blind 
  ends, 
  for 
  the 
  most 
  part 
  in 
  contact 
  with 
  one 
  another, 
  and 
  protected 
  

   by 
  special 
  spicules, 
  form 
  the 
  outer 
  surface 
  of 
  the 
  sponge. 
  Abundant 
  small 
  interstices 
  

   are 
  left 
  between 
  the 
  ends 
  of 
  the 
  radial 
  tubes, 
  which 
  serve 
  for 
  the 
  admission 
  of 
  

   water 
  into 
  the 
  irregular 
  interspaces 
  between 
  the 
  radial 
  tubes. 
  

  

  The 
  structure 
  of 
  the 
  individual 
  radial 
  tubes 
  is 
  shown 
  in 
  Figure 
  4, 
  

   Plate 
  v., 
  and 
  conforms 
  to 
  the 
  usual 
  Ascon 
  type. 
  The 
  inhalant 
  pores 
  (prosopyles) 
  are 
  

   very 
  distinctly 
  shown 
  in 
  my 
  preparations, 
  they 
  are 
  simply 
  circular 
  apertures 
  about 
  

   0.014 
  mm. 
  in 
  diameter. 
  

  

  The 
  interspaces 
  between 
  the 
  radial 
  tubes 
  are 
  wide 
  and 
  irregular, 
  widening 
  as 
  

   they 
  approach 
  the 
  wall 
  of 
  the 
  central 
  Ascon-tube. 
  

  

  By 
  cutting 
  off 
  portions 
  of 
  the 
  wall 
  of 
  the 
  central 
  Ascon-tube 
  and 
  staining 
  them 
  

   separately, 
  as 
  well 
  as 
  by 
  means 
  of 
  sections, 
  I 
  have 
  been 
  able 
  to 
  prove 
  beyond 
  doubt 
  

   that 
  the 
  central 
  cavity 
  of 
  the 
  sponge 
  is 
  really 
  lined 
  by 
  collared 
  cells 
  ; 
  its 
  wall 
  in 
  fact 
  

   presents 
  the 
  same 
  structure 
  as 
  those 
  of 
  the 
  radial 
  tubes 
  and 
  is, 
  like 
  the 
  latter, 
  

   perforated 
  by 
  inhalant 
  pores 
  (prosopyles). 
  

  

  According 
  to 
  Mr. 
  Carter 
  this 
  species 
  is 
  sometimes 
  lipostomous, 
  or 
  devoid 
  of 
  

   osculum. 
  He 
  says,* 
  describing 
  the 
  general 
  form 
  of 
  the 
  sponge, 
  " 
  conical, 
  rather 
  

   compressed, 
  sessile, 
  fixed, 
  with 
  cloaca 
  and 
  wide 
  mouth 
  ; 
  or 
  ovoid 
  and 
  free, 
  with 
  

   cloacal 
  cavity 
  but 
  iw 
  moutli, 
  that 
  is 
  H^ckel's 
  *Auloplegma'-form." 
  If 
  Mr. 
  Carter's 
  

   account 
  be 
  correct 
  it 
  is 
  a 
  very 
  remarkable 
  thing, 
  and 
  I 
  cannot 
  at 
  all 
  understand 
  how 
  

   the 
  stream 
  of 
  water 
  is 
  kept 
  up 
  through 
  the 
  sponge 
  when 
  there 
  is 
  no 
  osculum. 
  

  

  *Annals 
  and 
  Magazine 
  of 
  Natural 
  History, 
  June, 
  1886, 
  p. 
  505. 
  

  

  