﻿SPONGIIDA. 
  389 
  

  

  rounding 
  tissues. 
  The 
  paler 
  colour, 
  to 
  the 
  natural 
  eye, 
  of 
  the 
  latter 
  

   sponge 
  appears 
  to 
  be 
  due 
  to 
  the 
  greater 
  concentration 
  of 
  the 
  pigment 
  

   within 
  the 
  cells 
  : 
  a 
  similar 
  effect 
  is 
  produced 
  by 
  a 
  similar 
  cause 
  in 
  

   some 
  Cephalopoda 
  {Loligo). 
  

  

  IG. 
  Dysidea 
  digitifera. 
  (Plate 
  XLI. 
  fig. 
  C.) 
  

  

  Curved 
  and 
  anastomosing 
  cylindrical 
  digitations, 
  about 
  3 
  millira. 
  

   in 
  diameter, 
  arising 
  from 
  the 
  upper 
  aspect 
  of 
  an 
  erect, 
  compressed, 
  

   irregular 
  basal 
  mass, 
  and 
  tapering 
  gradually 
  to 
  pointed 
  ends. 
  Sur- 
  

   face 
  even, 
  minutely 
  roughened 
  by 
  the 
  presence 
  in 
  the 
  dermis 
  of 
  a 
  

   coarse, 
  reticulate, 
  horizontal 
  skeleton. 
  Yents 
  few, 
  scattered 
  on 
  main 
  

   mass 
  of 
  sponge, 
  subcircular, 
  leading 
  deeply 
  into 
  sponge. 
  Textnre 
  

   (in 
  spirit) 
  very 
  friable 
  ; 
  colour 
  pale 
  greyish 
  brown. 
  Main 
  skeleton 
  

   composed 
  of 
  large 
  foreign 
  bodies, 
  united 
  by 
  a 
  thin, 
  almost 
  colourless 
  

   membrane 
  (not 
  visible 
  unless 
  the 
  fibre 
  is 
  broken) 
  ; 
  primary* 
  fibres 
  

   running 
  approximately 
  at 
  right 
  angles 
  to 
  surface 
  ; 
  secondaries 
  

   {tertiunj 
  of 
  Marshall) 
  approximately 
  parallel 
  to 
  surface, 
  very 
  short 
  ; 
  

   meshes 
  narrow, 
  about 
  -07 
  to 
  -09 
  millim. 
  broad, 
  rounded 
  ; 
  fibres 
  -019 
  

   to 
  -Oo 
  millim. 
  thick. 
  Dermal 
  skeleton 
  formed 
  of 
  fibre 
  similar 
  to 
  

   that 
  of 
  the 
  main 
  skeleton, 
  about 
  -025 
  to 
  -055 
  millim. 
  thick, 
  forming 
  

   circular 
  or 
  oval 
  meshes, 
  -032 
  to 
  "09 
  millim. 
  broad. 
  Sarcode 
  pale 
  

   greyish 
  brown, 
  rather 
  granular. 
  

  

  Bah. 
  Albany 
  Island, 
  Torres 
  Straits, 
  8 
  fms. 
  

  

  This 
  is 
  a 
  delicate 
  species, 
  distinguished 
  from 
  all 
  other 
  described 
  

   species 
  by 
  its 
  closed 
  digitate 
  processes 
  (those 
  of 
  D. 
  callosa. 
  Marshall, 
  

   bear 
  vents) 
  ; 
  in 
  being 
  devoid 
  of 
  connli 
  it 
  differs 
  from 
  most 
  species, 
  

   but 
  seems 
  to 
  agree 
  with 
  Diisklea 
  lirl-ii, 
  Carter 
  (Ann. 
  & 
  Mag. 
  N. 
  H. 
  

   (5) 
  vii. 
  p. 
  374), 
  ? 
  Bowerbank. 
  

  

  Height 
  of 
  sponge 
  40 
  millim. 
  (1^ 
  inch) 
  ; 
  greatest 
  lateral 
  extension 
  

   25 
  millim. 
  (1 
  inch) 
  : 
  longest 
  individual 
  digitation, 
  20 
  millim. 
  

   (4 
  inch). 
  The 
  sponge 
  has 
  grown 
  up 
  amongst 
  and 
  over 
  some 
  speci- 
  

   mens 
  of 
  Eudendriam. 
  

  

  17. 
  Dysidea 
  semicanalis. 
  (Plate 
  XLT. 
  fig. 
  B.) 
  

   A 
  hollow 
  flattened 
  vertical 
  common 
  stem, 
  giving 
  rise 
  to 
  several 
  

   vertical 
  cloacal 
  tubes, 
  some 
  of 
  which 
  are 
  open 
  on 
  one 
  side 
  (evi- 
  

   dently 
  formed 
  in 
  some 
  cases 
  by 
  the 
  folding 
  over 
  of 
  surface-ridges), 
  

   united 
  more 
  or 
  less 
  by 
  their 
  projecting 
  knife-like 
  adjacent 
  edges. 
  Tubes 
  

   about 
  GO 
  millim. 
  {2^ 
  inches) 
  in 
  greatest 
  length 
  ; 
  mean 
  internal 
  dia- 
  

   meter 
  about 
  G 
  millim. 
  ; 
  contracted 
  at 
  mouth, 
  their 
  walls 
  3 
  to 
  4 
  millim. 
  

   in 
  greatest 
  thickness 
  ; 
  inner 
  surface 
  provided 
  with 
  a 
  few 
  shallow 
  

   pits. 
  Outer 
  surface 
  bearing 
  a 
  few 
  long, 
  but 
  not 
  prominent, 
  ridges 
  

   running 
  from 
  near 
  base 
  to 
  near 
  the 
  upper 
  end; 
  surface 
  between 
  ridges 
  

   even, 
  minutely 
  honeycombed 
  in 
  dry 
  state 
  by 
  small, 
  longitudinally 
  

   elongated 
  spaces, 
  separated 
  by 
  fibres 
  of 
  dermal 
  skeleton, 
  and 
  about 
  5 
  

   millim. 
  in 
  their 
  smaller 
  diameter. 
  Texture, 
  in 
  dry 
  state, 
  rather 
  harsh 
  

   to 
  the 
  touch, 
  firm 
  but 
  elastic, 
  compressible 
  and 
  somewhat 
  tough. 
  

   Colour 
  pale 
  yellowish 
  brown. 
  

  

  * 
  Secondary 
  of 
  Marshall, 
  primary 
  of 
  Hyatt, 
  vertical 
  of 
  Carter. 
  

  

  