﻿60 
  A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  Subsection 
  1. 
  Indivisn. 
  

  

  The 
  gastral 
  cavities 
  of 
  the 
  Ascon-tubes 
  composing 
  the 
  colony 
  retain 
  the 
  

   primitive 
  hollow 
  condition, 
  there 
  being 
  no 
  ingrowth 
  of 
  the 
  mesoderm 
  or 
  endoderm. 
  

  

  4. 
  Lciicosolenin 
  duhia, 
  n, 
  sp. 
  

  

  (PL 
  I., 
  Fig. 
  3 
  ; 
  PI. 
  IX., 
  Fig. 
  3.) 
  

  

  {a.) 
  General 
  Appearance 
  and 
  Canal 
  System. 
  — 
  The 
  sponge-colony 
  forms 
  irregular, 
  

   low-growing 
  masses, 
  composed 
  of 
  a 
  network 
  of 
  branching 
  and 
  anastomosing, 
  more 
  or 
  

   less 
  cylindrical 
  Ascon-tubes. 
  The 
  size 
  of 
  the 
  interspaces 
  between 
  the 
  tubes 
  varies 
  

   greatly 
  in 
  different 
  specimens 
  and, 
  indeed, 
  in 
  different 
  parts 
  of 
  the 
  same 
  specnnen. 
  

   No 
  definite 
  external 
  skin 
  (pseudoderm) 
  is 
  formed, 
  the 
  interspaces 
  between 
  the 
  surface 
  

   tubes 
  being 
  as 
  wide 
  as 
  in 
  the 
  interior 
  of 
  the 
  colony. 
  In 
  compact 
  colonies 
  the 
  surface 
  

   has 
  a 
  curious 
  vermiculated 
  appearance, 
  in 
  loose 
  ones 
  (PL 
  I., 
  Fig. 
  3) 
  it 
  is 
  a 
  lattice-work 
  

   with 
  oval 
  or 
  rounded 
  meshes. 
  On 
  the 
  under 
  surface 
  of 
  the 
  colony 
  are 
  sometimes 
  

   present 
  little 
  root-like 
  processes, 
  which 
  serve 
  for 
  attachment. 
  The 
  oscula, 
  when 
  

   discoverable, 
  are 
  visible 
  as 
  very 
  small, 
  round 
  apertures, 
  situate 
  on 
  the 
  apices 
  of 
  small 
  

   papillae 
  formed 
  by 
  the 
  anastomosis 
  of 
  several 
  Ascon-tubes. 
  

  

  The 
  diameter 
  of 
  the 
  cylindrical 
  Ascon-tubes 
  varies 
  a 
  good 
  deal 
  in 
  different 
  parts 
  

   of 
  the 
  same 
  colony, 
  say 
  from 
  0.5 
  to 
  1 
  mm. 
  To 
  the 
  naked 
  eye 
  some 
  of 
  the 
  tubes 
  

   appear 
  smooth 
  on 
  the 
  outer 
  surface, 
  others 
  minutely 
  but 
  distinctly 
  hispid. 
  The 
  

   colour 
  in 
  spirit 
  is 
  white 
  or 
  nearly 
  so. 
  Further 
  details 
  as 
  to 
  the 
  canal 
  system, 
  which 
  

   conforms 
  to 
  type 
  A, 
  will 
  be 
  found 
  on 
  p. 
  28. 
  

  

  {b.) 
  Arrangement 
  of 
  the 
  Skeleton. 
  — 
  The 
  skeleton 
  consists 
  of 
  triradiate 
  and 
  

   oxeote 
  spicules. 
  The 
  former 
  are 
  arranged 
  in 
  a 
  confused 
  layer 
  in 
  the 
  mesoderm, 
  the 
  

   spicules 
  being 
  placed 
  close 
  together 
  with 
  rays 
  overlapping. 
  The 
  latter 
  occur 
  only 
  in 
  

   certain 
  parts 
  of 
  the 
  colony, 
  namely, 
  in 
  some, 
  and 
  apparently 
  only 
  some, 
  of 
  the 
  

   outer 
  Ascon-tubes. 
  Hence 
  a 
  boiled 
  out 
  preparation 
  from 
  one 
  part 
  of 
  a 
  specimen 
  

   may 
  show 
  no 
  oxeote 
  spicules 
  at 
  all, 
  while 
  another 
  from 
  a 
  different 
  part 
  of 
  the 
  same 
  

   specimen 
  contains 
  plenty 
  of 
  them. 
  When 
  present 
  the 
  oxeotes 
  project 
  more 
  or 
  less 
  

   from 
  the 
  outer 
  surface 
  of 
  the 
  Ascon-tubes, 
  whence 
  the 
  hispid 
  appearance 
  of 
  the 
  latter. 
  

  

  (c.) 
  The 
  Spicules 
  (PL 
  IX., 
  Fig. 
  3.) 
  

  

  (L) 
  Triradiates.— 
  These 
  are 
  approximately 
  regular 
  or 
  slightly 
  sagittal. 
  

   The 
  rays 
  are 
  fairly 
  stout, 
  conical 
  or 
  subfusiform 
  in 
  shape, 
  fairly 
  

   sharply 
  but 
  rather 
  abruptly 
  pointed, 
  often 
  a 
  little 
  irregular 
  in 
  diameter 
  

   and 
  mode 
  of 
  pointing 
  ; 
  measuring 
  about 
  0-18 
  by 
  0-014 
  mm. 
  

  

  