﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  II.— 
  THE 
  OKGANISATION 
  OF 
  THE 
  CALCAEEA 
  HOMOCCELA. 
  

   A. 
  — 
  The 
  Olynthus 
  Type. 
  

  

  In 
  the 
  hope 
  that 
  the 
  present 
  work 
  may 
  be 
  of 
  use 
  to 
  naturahsts, 
  and 
  especially 
  

   Australian 
  naturalists, 
  who 
  are 
  not 
  professed 
  spongologists, 
  I 
  propose 
  to 
  deal 
  more 
  

   in 
  detail 
  with 
  the 
  anatomical 
  side 
  of 
  the 
  question 
  than 
  would 
  otherwise 
  be 
  necessary, 
  

   and 
  to 
  commence 
  by 
  describing 
  briefly 
  what 
  may 
  be 
  regarded 
  as 
  the 
  simplest 
  and 
  

   most 
  typical 
  form 
  of 
  organisation 
  met 
  with 
  in 
  the 
  group. 
  We 
  may 
  then 
  investigate 
  

   the 
  more 
  readily 
  in 
  what 
  manner 
  and 
  to 
  how 
  great 
  an 
  extent 
  the 
  other 
  members 
  of 
  

   the 
  group 
  differ 
  from 
  this 
  typical 
  form. 
  

  

  The 
  simplest 
  type 
  of 
  organisation 
  met 
  with 
  in 
  the 
  group 
  is 
  known 
  by 
  HcBckel's 
  

   term 
  ^' 
  OlyiUhus" 
  ,* 
  and 
  this 
  name 
  may 
  conveniently 
  be 
  retained 
  for" 
  the 
  type 
  of 
  

   organisation 
  in 
  question, 
  though 
  not 
  as 
  indicating 
  a 
  "genus" 
  in 
  the 
  ordinarily 
  

   accepted 
  meaning 
  of 
  that 
  term. 
  

  

  In 
  the 
  Olynthus 
  type, 
  then, 
  the 
  sponge 
  consists 
  of 
  a 
  small, 
  thin-walled 
  tube 
  or 
  

   sac, 
  the 
  lower 
  end 
  of 
  which 
  is 
  closed 
  and 
  attached 
  to 
  some 
  foreign 
  object, 
  while 
  at 
  

   the 
  upper 
  end 
  is 
  a 
  large 
  opening 
  known 
  as 
  the 
  oscidiiin. 
  The 
  wall 
  of 
  the 
  tube, 
  

   moreover, 
  is 
  perforated 
  by 
  numerous 
  A'ery 
  minute 
  apertures 
  known 
  as 
  the 
  inhalant 
  

   pores 
  or 
  prusopyles.\- 
  The 
  prosopyles, 
  the 
  cavity 
  of 
  the 
  tube 
  {gastral 
  cavity), 
  and 
  the 
  

   osculum 
  together 
  constitute 
  what 
  is 
  known 
  as 
  the 
  canal 
  system 
  of 
  the 
  sponge, 
  here 
  

   met 
  Avitli 
  in 
  its 
  simplest 
  condition. 
  

  

  The 
  wall 
  of 
  the 
  tube 
  is 
  made 
  u}) 
  of 
  three 
  distinct 
  layers. 
  On 
  the 
  outside 
  is 
  a 
  

   single 
  layer 
  of 
  flattened, 
  plate-like, 
  nucleated 
  epithehal 
  cells, 
  polygonal 
  in 
  shape 
  and 
  

   in 
  contact 
  with 
  one 
  another 
  at 
  their 
  edges 
  ; 
  this 
  layer 
  is 
  known 
  as 
  the 
  ectudfi'iii. 
  On 
  

   the 
  inside 
  is 
  a 
  single 
  layer 
  ol" 
  " 
  collared 
  cells 
  " 
  known 
  as 
  the 
  emloderm, 
  and 
  between 
  

   the 
  cndodcnn 
  and 
  ectoderm 
  is 
  the 
  incsudenii, 
  consisting 
  of 
  a 
  layer 
  of 
  gelatinous 
  

   material 
  in 
  whicli 
  are 
  embedded 
  the 
  skeleton 
  of 
  the 
  sponge 
  (consisting 
  of 
  calcareous 
  

   spicules) 
  and 
  various 
  kinds 
  of 
  cells. 
  

  

  The 
  histological 
  characters 
  of 
  tliese 
  three 
  fundamental 
  layers 
  will 
  be 
  described 
  in 
  

   detail 
  later 
  on, 
  meanwhile 
  it 
  is 
  important 
  to 
  remember 
  that 
  these 
  three 
  layers 
  are 
  

   found 
  in 
  all 
  sponges 
  and 
  that 
  they 
  always 
  exhibit 
  the 
  same 
  essential 
  eliaracteristies, 
  

   although 
  numerous 
  differences 
  in 
  detail 
  are 
  met 
  with. 
  

  

  • 
  " 
  Die 
  Kalksohwumme," 
  Vol. 
  1, 
  p. 
  21'J 
  ik-. 
  Vol. 
  3, 
  Plate 
  1, 
  L'ig. 
  1. 
  

  

  I 
  The 
  fenii 
  " 
  piosopjlc 
  " 
  is 
  used 
  by 
  Sollas, 
  in 
  liis 
  article 
  on 
  Sponges 
  in 
  tlio 
  " 
  Eiicyclopuiliii 
  Britiuinicn," 
  to 
  

   ileBignate 
  the 
  oiieiiiiiKs 
  of 
  Iho 
  inhalant 
  cunuls 
  into 
  the 
  llai^elhUiHl 
  uhanilieis 
  and 
  to 
  distinguish 
  them 
  from 
  the 
  inhalant 
  

   pores 
  on 
  the 
  surface 
  of 
  the 
  apongc. 
  In 
  a 
  thinwalled 
  Ol.yntluis 
  the 
  inhalant 
  pores 
  and 
  prosopyles 
  are 
  so 
  close 
  together 
  

   that 
  iliey 
  may 
  for 
  all 
  practical 
  i)urposes 
  bo 
  regarded 
  as 
  identical. 
  In 
  higher 
  forms, 
  however, 
  it 
  is 
  very 
  convenient 
  to 
  have 
  

   distinct 
  names 
  for 
  the 
  two 
  structures. 
  

  

  