﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  27 
  

  

  tubes 
  in 
  the 
  interior 
  of 
  the 
  colony. 
  The 
  pseudoderm 
  is 
  also 
  perforated 
  by 
  

   larger 
  exhalant 
  openings 
  (oscula 
  or 
  pseiidosciila). 
  

  

  Subdivision 
  1. 
  — 
  The 
  exhalant 
  openings, 
  through 
  which 
  the 
  water 
  leaves 
  

   the 
  sponge, 
  are 
  true 
  oscula, 
  i.e., 
  they 
  lead 
  directly 
  into 
  a 
  space 
  lined 
  

   by 
  collared 
  cells 
  and 
  formed 
  by 
  the 
  union 
  of 
  a 
  number 
  of 
  Ascon- 
  

   tubes. 
  

  

  Type 
  B., 
  canal 
  system 
  normal. 
  

  

  Examples. 
  — 
  Leucosoleiiia 
  stipitata, 
  n. 
  sp.. 
  Leucosolenia 
  

   pidcherrima, 
  n. 
  sp. 
  

  

  Type 
  C, 
  canal 
  system 
  reversed. 
  

  

  Example. 
  — 
  Leucosolenia 
  cavata, 
  Carter 
  sp. 
  

  

  Subdivision 
  2. 
  — 
  The 
  exhalant 
  openings 
  through 
  which 
  the 
  water 
  leaves 
  

   the 
  sponge 
  are 
  pseudoscula, 
  i.e., 
  they 
  lead 
  at 
  hrst 
  into 
  a 
  space 
  not 
  lined 
  

   by 
  collared 
  colls, 
  but, 
  presumably, 
  by 
  ectoderm. 
  This 
  space 
  is 
  a 
  

   pseudogaster, 
  it 
  really 
  lies 
  outside 
  the 
  colony 
  and 
  is 
  formed 
  probably 
  

   by 
  the 
  upgrowth 
  of 
  the 
  colony 
  around 
  it. 
  The 
  Ascon- 
  tubes 
  open 
  

   into 
  the 
  pseudogaster. 
  

  

  Type 
  D., 
  with 
  the 
  characters 
  of 
  the 
  subdivision. 
  

  

  Example. 
  — 
  Leucosolenia 
  ventricosa, 
  Carter 
  sp. 
  

  

  Subsection 
  2. 
  Subdivisa. 
  

  

  The 
  gastral 
  cavities 
  of 
  the 
  Ascon-tubes 
  are 
  more 
  or 
  less 
  subdivided 
  into 
  

   incomplete 
  chambers 
  l)y 
  ingrowths 
  of 
  mesoderm, 
  or 
  of 
  both 
  mesoderm 
  and 
  

   endoderm. 
  

  

  Type 
  E. 
  — 
  The 
  collared 
  cells 
  liave 
  not 
  yet 
  spread 
  in 
  over 
  the 
  

   ingrowths 
  of 
  mesoderm. 
  

  

  Example. 
  — 
  Leucosolenia 
  proxima, 
  n. 
  sp. 
  

  

  Type 
  F. 
  — 
  The 
  collared 
  cells 
  have 
  spread 
  in 
  over 
  the 
  ingrowths 
  of 
  

   mesoderm. 
  

  

  Examples. 
  — 
  Leucosolenia 
  icilsoni, 
  n. 
  sp. 
  Leucosolenia 
  

   depi'cssa, 
  ii. 
  s}). 
  

  

  Having 
  thus 
  brielly 
  rc\ic\V(-d 
  the 
  six 
  typos 
  of 
  canal 
  system 
  which 
  1 
  have 
  found 
  

   amongst 
  the 
  Victorian 
  reticulate 
  Homoca'la 
  we 
  may 
  pass 
  on 
  to 
  describe 
  somewhat 
  

   more 
  in 
  detail 
  an 
  example 
  of 
  each. 
  

  

  